Basic Entomology. Chapter 6. Bob Polomski and Eric Benson, Ph.D.

Transcription

1 Chapter 6 Basic Entomology Bob Polomski and Eric Benson, Ph.D. Learning Objectives Be familiar with the standard classification system (from phyla to species and common names) Know the basic form and structure (morphology) of insects and how knowledge of these are useful for identification and choices for pest control. Define metamorphosis and the different types. Know the benefits and value of insects. Know the various types of insect injury. Know the steps to take to identify any insect. Be able to identify the most common beneficial insects. Have an appreciation for how proper insect identification fits into a pest management plan. Collect, preserve, and ship a useful insect specimen and be able to collect data and insect/plant sample in order to properly send the Insect Identification and Diagnosis Request form to Clemson University for identification and management recommendation. Basic Entomology 129

2 Basic Entomology Insects are among the oldest, most numerous, and most successful creatures on earth. About one million different species are known to exist, occupying every conceivable habitat except for the open ocean. Insects can be found in or on animals, plants, soil, streams, lakes, ocean shores, in wooden structures and furniture, and in stored grains and other foods. While insects that cause problems for humans receive the most publicity, the vast majority are either beneficial or harmless. Insects pollinate most fruits and vegetables. They provide food for many animals. Some produce useful products such as honey, wax, shellac, and silk. In addition, some insects are beneficial because they feed on other insect pests. Worldwide, only about one percent of known insect species (or about 10,000) are economically destructive pests. These harmful insects destroy crops in the field and in storage. About one-sixth of the world s food crops are eaten by insects. They also transmit diseases to crops, livestock, pets, and humans. Insects and Their Relatives Insects belong to the phylum Arthropoda, which means jointed legs. This phylum includes spiders, ticks, crabs, and lobsters. Arthropods have segmented bodies and a skeleton outside of the body, which is called an exoskeleton. There are a number of arthropods that are mistakenly called insects. These insect relatives include mites and spiders (arachnids), centipedes (chilopods), sowbugs and pillbugs (crustaceans), millipedes (diplopods), and snails and slugs (molluscs). Illustrations and brief descriptions of these insect relatives can be found in the Common Noninsects section on p Insect Anatomy For an organism to be classified as an insect, the adult form must have six legs and three distinct body regions (Figure 6.1). In addition, most (but not all) adult insects have one or two pairs of wings located on the second or third segment of the thorax. Jointed legs (3 pairs) The most important characteristic of insects is the presence of three pairs of jointed legs. These are almost always present on adult or mature insects and are generally present in the other stages as well. In addition to walking and jumping, insects often use their legs for digging, grasping, feeling, swimming, carrying loads, building nests, and cleaning parts of the body. The legs of insects vary greatly in size and form and are used in classification (Figure 6.2). Figure 6.1 The body parts of a typical insect. compound eye antennae jumping head thorax abdomen Figure 6.2 Leg adaptations of some insects. walking or running wings legs digging grasping carrying Basic Entomology 130

3 Distinct body regions The adult insect s body is made up of three parts: head, thorax, and abdomen (Figure 6.1). An insect s body is not supported by a bony skeleton but by a tough body wall or exoskeleton. The tough covering of skin is referred to as the cuticle. The cuticle contains a layer of wax that determines its permeability to water (even to insecticides) and prevents desiccation or drying. The cuticle of each segment is formed into several hardened plates called sclerites, separated by infolds or sutures which provide flexibility. The cuticle of the immature or larval stage is not usually as hardened as that of the adult. The thorax is made up of three segments: prothorax, mesothorax, and metathorax. Each of these segments bears a pair of legs. The wings are attached to the mesothorax and metathorax, never to the prothorax or first segment. The abdomen may have 11 or 12 segments, but in most cases they are difficult to distinguish. Some insects have a pair of appendages at the tip of the abdomen. They may be short, as in grasshoppers, termites, and cockroaches; extremely long, as in mayflies; or curved, as in earwigs. Insects breathe through pores in their abdomens called spiracles. Some insecticides enter the insect pest s body through the spiracles. Antennae (1 pair) The main features of an insect s head are the eyes, antennae, and mouthparts. The antennae are a prominent and distinctive feature of insects. Figure 6.3 Various kinds of antennae. Plumose Figure 6.4 Some insect wings showing venation. Insects have one pair of antennae located on the adult s head usually between or in front of the eyes. Antennae are segmented, vary greatly in form and complexity, and are often referred to as horns or feelers (Figure 6.3). They are primarily organs of smell but serve other functions in some insects. Wings Many insects develop wings as adults, and so are recognized as the only winged arthropods. The names of some of the insect orders end in -ptera, which comes from the Greek word meaning with wings. Thus, each of these names denotes some feature of the wings. Hemiptera (true bugs) means half-winged; Hymenoptera (ants, bees, and wasps) means membrane-winged; Diptera (flies) means two-winged; and Isoptera (termites) means equalwinged. The venation or the arrangement of veins in wings is different for each species of insect; thus, it serves as a means of identification (Figure 6.4). Systems have been devised to designate the venation for descriptive purposes. Wing surfaces may be covered with fine hairs or scales, or they may be bare. Aristate Clavate Serrate Filiform Lamellate Pectinate Moniliform Setaceous Mouthparts An insect s most remarkable and complicated structural feature is its mouth. Many variations exist in the form and function of insect mouthparts. And although insect mouthparts differ considerably in appearance, the same basic parts are found in all types. Most insects are divided into two broad categories by mouthpart type: either adapted for sucking or chewing (Figure 6.5). One exception is the sponging mouthparts on many species of flies. Insects with chewing mouthparts have Basic Entomology 131

4 Figure 6.5 Examples of insects with sucking mouthparts (A), and chewing mouthparts (B). (A) Sucking mouthparts- -cicada - mandibles with teeth and strong jaws. Chewing larvae and adults bite and chew plant parts creating holes and tunnels in leaves, stems, twigs, and fruits (Figure 6.6). Chewing damage is done inside stems and branches by borers, inside leaves by miners, in fruits, nuts, or seeds by worms or weevils; and on leaves by defoliators or skeletonizers. Some common examples of insects that cause injury by chewing include armyworms, cabbageworms, Colorado potato beetles, grasshoppers, Japanese beetles, and fall webworms Insect pests with sucking mouthparts pierce plants with slender, sharp-pointed mouthparts called stylets and suck plant sap. These insects, which include aphids, leafhoppers, scale insects, true bugs, scale insects, thrips, and whiteflies, feed on photosynthates, or the products of photosynthesis (sugars and other complex carbohydrates). The withdrawal of the sap results in minute white, brown, or red spotting on leaves, fruits, or twigs; curling leaves; deformed fruit; or general wilting, browning, and dying of the entire plant. Some of these insects inject toxic salivary products into the plant that results in discolored leaves and dieback of woody plant parts. Some insects, such as aphids and leafhoppers, are vectors or transmitters of diseases, especially viruses. When they feed on a diseased plant, Basic Entomology 132 (B) Chewing mouthparts- -grasshopper Figure 6.6 Insects and feeding injury. Leaf galls Mites Damage by leaf-chewing insects Lacebug they transmit the disease to another host plant when their saliva mixes with the sap. The damage done by sucking mouthparts seldom results in loss of plant tissue. Rather, holes or deformed growth occur. Pests with chewing mouthparts remove plant tissue. Knowing the difference in damage caused by chewing or sucking insects is the first step in pest identification. The mouthparts of larvae tend to be different from the adults of the same species because they feed on different foods. Caterpillars have chewing mouthparts for consuming leaves and other vegetation. In contrast, adult moths or butterflies feed on liquids, such as nectar, so they are equipped with a sucking tube that forms siphoning mouthparts. Insects that attack plants below the soil surface have chewing or sucking mouthparts. The attacks differ from the above-ground forms only in their po- Shoot moth larva Twig galls Wood borers Adult Larva Twig girdler Tent caterpillar egg mass Bark beetle Serpentine leaf miners Scale insects Aphids Blotch leaf miners Root-feeding white grub

5 sition with reference to the soil surface. Some subterranean insects spend their entire life cycle below ground. For example, the woolly apple aphid, as both nymph and adult, sucks sap from the roots of apple trees, causing the development of tumors and subsequent decay of the tree s roots. Other subterranean insects have at least one life stage above ground. Examples include wireworms, root maggots, strawberry root weevils, blackvine weevils, Japanese beetles, and grape and corn rootworms. The larvae are root feeders while the adults live above-ground. Insect Growth and Development Every insect begins life as an egg; however, the eggs of some harmful pests, such as aphids, hatch within the body of the female parent and the immatures are born as living young insects. In some insects, the egg may or may not need to be fertilized by sperm to develop. Females can produce more females (or males, in some cases) by a process called parthenogenesis. Bees, ants, wasps, and aphids are notable examples of insects that can reproduce by parthenogenesis. When males are required, sexual mating takes place. Insects grow by shedding their outer skin or exoskeleton in a process called molting. Insects increase in size and appearance with each molt. Immature insects may molt many times, some six times or more. This change in shape and appearance from the juvenile to the adult stage is called metamorphosis (Figure 6.7). The term is a combination of two Greek words: meta, meaning change, and morphe, meaning form. It is commonly defined as a marked or abrupt change in form or structure Figure 6.7 Insect development: metamorphosis. Examples Orders: Collembola Diplura Protura Thysanura Orders: Dermaptera Hemiptera Homoptera Isoptera Orthoptera Thysanoptera Orders: Ephemeroptera Odonata Plecoptera Orders: Coleoptera Diptera Hymenoptera Lepidoptera Neuroptera Siphonaptera Nonmetamorphosis Egg Young Adult Simple metamorphosis Egg Nymphs Adult Incomplete metamorphosis Egg Naiads Adult Complete metamorphosis Egg Larvae Pupa Adult and refers to all stages of development. Related arthropods such as spiders, mites, and centipedes also undergo metamorphosis; however, the changes in shape of spiders and lower insects are much less dramatic than the complete change in shape of the more developed kinds of insects. This change is called complete metamorphosis. Beetles, moths, butterflies, wasps, ants, and flies all go through four very different stages in order to complete development: egg, larva, pupa, and adult. The larva is often the damaging stage because it is basically a feeding machine. Over time, the larva or nymph sheds its exoskeleton (molts) at various stages of growth because it outgrows the hard covering or cuticle. Most insects do not grow gradually but by stages. When their exoskeleton Basic Entomology 133

6 Basic Entomology 134 Insects as Transmitters of Plant Diseases In 1892, it was discovered that the plant disease fireblight of fruit trees was spread by honeybees. At present there is evidence that more than 200 plant diseases are transmitted by insects (Table 6.1). About 150 of these diseases are viruses, 25 or more are caused by fungi, 15 or more by bacteria, and a few are caused by protozoa. Insects may spread plant diseases in various ways: By feeding, laying eggs, or boring into plants, they create an entrance point for a disease they do not actually carry. They carry the disease on or in their bodies from one plant to a susceptible surface of another plant, such as a flower or a wound made by some other agent. They carry pathogens on the outside or inside of their bodies and inject plants as they feed. An insect may serve as an essential host for some part of the pathogen s life cycle, and the disease cannot complete its life cycle without the host. gets too tight, it splits open and the insect crawls out, protected by a new and larger exoskeleton that has formed underneath the old one. The stage of life between each molt is called an instar. Following each molt, the insect increases its feeding. The number of instars, or frequency of molts, varies considerably with species and, to some extent, with food supply, temperature, and moisture. Feeding by adults may be destructive as well. The larval and adult stages of many species feed on different hosts or different parts of the host. The pupal stage does not feed and appears to be inactive, but is actually in a very active stage of metamorphosis. The lower insects undergo a slight change of shape which is called simple metamorphosis. True bugs, aphids, grasshoppers, termites, earwigs, and some aquatic insects, go through only three stages in order to complete development. These are egg, nymph, and adult. Nymphs and adults closely resemble each other, except the nymphs are smaller in size and lack wings. In these species, the adults and nymphs usually feed on the same host or host parts. In some aquatic insect species, such as dragonflies, the nymphs are gill-breathing, making them Table 6.1 Examples of insect-vectored (insect-transmitted) plant diseases. Disease...Vector Dutch elm disease (fungus)...elm bark beetle Fireblight (bacteria)...pollinating insects Tomato curly top virus...beet leafhopper Cucumber mosiac virus...aphids Tomato spotted wilt virus...thrips Yellows virus...whiteflies more different in appearance, and in their habitat, compared to adults. Insects in this group are sometimes referred to as having incomplete metamorphosis, and the nymphs are sometimes called naiads. The most primitive insects go through very little change between stages. The adults lack wings, so they closely resemble the nymphs. Most experts refer to this as nonmetamorphosis. A life cycle from the egg to the production of an egg by the subsequent adult stage is called a generation. Many insect species only have one generation each year, while others have several especially in the south where warm seasons last longer. A single generation may require many years, such as 17 years for some cicadas, one of the longest-lived insects in North America. A new generation does not always begin with the egg stage in the spring. However, in any given region, an insect species normally overwinters in the same stage each year. Insects are cold-blooded and their body temperature is influenced by the surrounding temperature of their environment. Winter in South Carolina offers gardeners some respite from insects. A majority of insects are active during the warmer months of the year or during warmer parts of the day. Insect Classification and Identification Identifying the hundreds of thousands of known insect species would be impossible if they were not organized around a standard classification system. This system of grouping organisms is based on the degrees of similarity among them. It ranges from the broad-based Kingdom to the more specific Species level as shown below: Kingdom Phylum Class Order Family Genus Species/Specific epithet

7 This hierarchical classification system is also used to identify plants (Ch. 3, Basic Botany ). At the highest level, most organisms are divided into two kingdoms: animal and plant. The animal kingdom has major divisions known as phyla (phylum is singular). Several of the following phyla contain agricultural pests: Arthropods (insects, spiders, crayfish, millipedes) Aschelminthes (round worms, trichina) Platyhelminthes (flatworms, flukes, tapeworms) Mollusca (snails, slugs, clams). Specific Insect Orders The phylum Arthropoda is divided into classes. Table 6.2 describes a few of the more important classes and presents characteristics used to distinguish between the groups. Insects belong to the Class Hexopoda. The Class Hexopoda is further subdivided into 31 categories called orders. Each order may contain dozens, hundreds, or thousands of species that share similar anatomical features or body parts. Some examples of insect orders include: Coleoptera: beetles and weevils Dermaptera: earwigs Diptera: Flies, mosquitos, gnats, and midges Hemiptera: true bugs, leafhoppers, aphids, scales, whiteflies Hymenoptera: Ants, bees, and wasps Isoptera: termites Lepidoptera: butterflies and moths Neuroptera: lacewings, antlions, etc. Odonata: damselflies and dragonflies Orthoptera: crickets, katydids, and grasshoppers Thysanoptera: Thrips The most important orders for gardeners are listed in Table 6.3. Not all of the insects in this table are plant-feeding pests, even when you find them on a plant. For example, insects in Coleoptera, Diptera, Hymenoptera and Neuroptera can be found on plants, as parasites or predators of plant-feeding insects, pollinators, or scavengers of dead vegetation or materials left behind by other insects. Insect orders are subdivided into smaller groups known as families, genera, and species. The family is a more finite grouping of very closely related insects. Family names end with idae. Aphidae (aphids), Aleyrodidae (whiteflies), and Chrysomelidae (leaf beetles) are examples of families of insects. Families are further subdivided into genera and species. These are usually the most finite levels of the classification system. Consider these examples for classifying two insects: Japanese beetle Order: Coleoptera Family: Scarabeaidae Genus: Popillia Species: japonica Euonymus Scale Order: Hemiptera Family: Diaspididae Genus: Unaspis Species: euonymi A majority of insect species have common names, which are often associated at the genus level. Most commonly found insects also acquire common names, and sometimes one species has several common names. For example, Helicoverpa zea, when found on corn, is called the corn earworm. When it is found on tomatoes, it is called the tomato fruit- Table 6.2 Classes of the phylum Arthropoda. Body Pairs Class Examples Segments of Legs Agricultural Importance Arachnida spiders, mites, 2 4 Some mites are major plant and ticks pests. Crustacea crayfish, 2 5 Sowbugs can be minor pests. sowbugs Hexopoda bugs, beetles, 3 3 Large numbers are pests. (Insecta) moths Symphyla symphylans 2 12 Can be serious pests. Basic Entomology 135

8 Ento-terminology Abdomen Antennae Compound eye Honeydew Larva Mandibles Metamorphosis Molt Nymph Ovipositor Parthenogenesis Parasite Pheromone Predator Prolegs Pupa Thorax Vector The hindmost of the three major divisions of the body, often composed of 11 segments and without either true legs or wings. Segmented appendages on the head, carrying sense organs for smelling and touching. An eye composed of many individual elements or ommaidia adapted for detecting movement. Anal secretions of aphids and other Homoptera; exudate of some galls. The active feeding and growing stages of the higher insects, preceding the pupal stage. The strong, chewing pair of mouthparts. The changes through which an insect passes from the young form to the adult. The shedding of the skin or exoskeleton during growth. The cast skin is called the exuvia; the intervals between molts are called stages or stadia; the form assumed during a particular stage is known as an instar. The active feeding and growing young stage of the less highly evolved insects. Insects with nymphs do not have a pupal stage. Tube from which the female deposits (oviposits) eggs. A form of asexual reproduction; development of an egg without fertilization. An organism that lives on or in another (host) organism and obtains all of its nutrients from that host, contributing nothing of benefit to the host. Substance emitted by an animal that causes a specific response from others, usually of the same species. An animal living at the expense of others; an insect predator differs from a parasite in that it usually requires more than one host. Fleshy unjointed false legs of caterpillars and the larvae of some sawflies, used in clinging to surfaces and for support in locomotion. The transformation stage between larva and adult of the more advanced insects. The middle section of three segments behind the head and in front of the abdomen. Comprised of three parts: prothorax, mesothorax, and metathorax. Each segment has one pair of legs; in addition, the mesothorax and metathorax each may carry one pair of wings. The large shield-like top side of the prothorax is know as the pronotum. The thorax is largely filled with powerful flight muscles. An insect that carries a disease organism from one plant to another. Basic Entomology 136

9 Table 6.3 Orders of the class Hexopoda encountered in the garden and landscape. Order Common Name Metamorphosis Mouthparts Wings Coleoptera beetles, weevils complete chewing 2 pair Collembola springtails none chewing none Dermaptera earwig simple chewing 2 pair Diptera flies complete chewing (some larvae), 1 pair sponging, or piercingsucking Hemiptera true bugs, aphids, scale simple piercing-sucking 2 pair Hymenoptera bees, wasps, ants complete chewing-lapping 2 pair Isoptera termites simple chewing 2 pair Lepidoptera butterflies, moths complete chewing (larvae) 2 pair or siphoning (adult) Neuroptera lacewings, dobsonflies complete chewing 2 pair Orthoptera crickets, grasshoppers simple chewing 2 pair Siphonaptera fleas complete chewing or none piercing-sucking Plant Injury Caused by Oviposition Probably 95% of insect injury to plants is caused by feeding, but plants can also be damaged when insects oviposit or lay eggs. For example, the periodical cicada deposits eggs in one-year-old growth of fruit and forest trees, splitting the wood so severely that the entire twig often dies. As soon as the young hatch, they desert the twigs and cause no further injury to the plant. In other cases, the offspring feed on the plant after hatching. The plum curculio ruins the fruits of apples, plums, and peaches when the female lays eggs in the fruit. Upon hatching, the larvae feed inside the fruit. Gall insects oviposit into plants and cause them to produce a structure of deformed tissue. The insect then finds shelter and abundant food inside this plant growth. The continued development results from secretions of the developing larva. Although galls are composed entirely of plant tissue, the insect controls and directs the form and shape they take as they grow. Besides laying eggs in plants, insects sometimes remove plant parts for constructing or provisioning nests. Leaf-cutter bees scissor out neatly cut circles at the leaf edges. These important pollinators, which look like small black bumblebees, are solitary bees. The females lay individual eggs and provision them with stores of pollen. They nest in hollow twigs or other natural cavities, using the leaf disks to line and cap each cell. Preferred leaves include roses, azaleas, and ash. While it may be difficult to admire such handiwork, leaf-cutter bees usually cause only cosmetic injury to plants. worm, and on cotton it is called the cotton bollworm. Common names are often used to refer to large families or orders of insects. For example, the order Lepidoptera refers to butterflies and moths, and the order Coleoptera refers to beetles. Common insect orders in the home and garden Coleoptera: Beetles and Weevils (Figure 6.8) Most adults have a hardened, horny outer skeleton. Most adults have two pairs of wings, the outer pair hardened and the inner pair membranous. (A few beetles are practically wingless, and some have only an outer hard pair of wings.) Chewing mouthparts. Adults usually have noticeable antennae. Larva has a head capsule, three pairs of legs on the thorax with no legs on the abdomen. (Weevil larva lacks legs on the thorax). Complete metamorphosis. Some are beneficial as pollinators or as predators of harmful insect species. Beetles are common insects (about 40% of all insect species), but only a few are garden pests. Flea beetles, wireworms (click beetle larvae), cucumber beetles, vegetable weevils, and green fruit beetles are common in South Carolina home vegetable Basic Entomology 137

10 Figure 6.8 Insects in the Order Coleoptera. Ground beetle Diving beetle Rove beetle Click beetle Carpet beetle Lady beetle Longhorn Bark beetle (abdomen). They usually use their pinchers to protect themselves from predators, but in some cases, they may use them to catch prey. Short, hardened outer wings; folded, membranous, ear-shaped inner wings. Adults and nymphs are similar in appearance. They are generally considered harmless creatures. Earwigs are active at night and will remain hidden under mulch, boards, rocks, woodpiles, and other cool damp places. Most earwigs only eat decaying plant material or dead insects. The European earwig is the most common species found in South Carolina and can be a nuisance. The striped earwig is another southern species that can be found in agricultural fields and gardens. These beneficial insects prey on many important pests, such as aphids, scales, and mites. Spider beetle Scarab Seed beetle Carrion beetle Weevil Leaf beetle Woodborer Flour beetle gardens. Boring beetles infest trunks and branches of fruit and nut trees. Adult pest beetles may feed on the same crop as their larvae, unlike other pest groups, such as caterpillars (larval stage of butterflies and moths) and maggots (fly larvae) where the adult stage does little damage. Ladybird beetles (ladybugs) feed on a wide range of pests including aphids, scale insects, insect eggs, mites, and other small insects. Dermaptera: earwigs (Figure 6.9) Adults are medium-sized, usually brown to black in color. Chewing mouthparts. Gradual metamorphosis. Elongate, flattened insects with strong, movable forceps on the abdomen. The adults have small wings and all earwigs, young and adults, have curved pinchers at the end of their bodies Basic Entomology 138 Diptera: flies, mosquitoes, gnats, and midges (Figure 6.10) Adults have only one pair of wings, usually soft-bodied and often hairy. Most adults have sponging (housefly) or piercing (mosquito) mouthparts. Larvae may have mouth hooks or chewing mouthparts. Most larvae are legless. Larvae of advanced forms, such as the house fly and relatives, have no head capsule, possess mouth hooks, and are called maggots; lower forms such as mosquito larvae and relatives have a head capsule. Complete metamorphosis. Hemiptera: Stink bugs, plant bugs, squash bugs, boxelder bugs, aphids, cicadas, leafhoppers, mealybugs, scale insects, and whiteflies (Figure Figure 6.9 Order Dermaptera Earwig

11 Figure 6.10 Insects in the Order Diptera. Crane fly Flower or Hover fly Mosquito Midge, Gnat, Punkie Vinegar fly Blow fly Tachinid fly Mydas fly 6.11) Very diverse group. Many are carriers of plant pathogens. Simple metamorphosis; stages are egg, nymph, and adult. All stages have sucking mouthparts. Adults and nymphs are often both damaging, if the species is a pest. Generally small to mediumsized insects; cicadas may be large and hard-bodied. Some are predators on harmful insect pests. Winged and wingless forms. fish scalelike covering produced by the tiny insect, which is about the size of a pencil tip. Scale insects anchor to plant parts by their piercing-sucking mouthparts and feed on plant sap. Individual scales may look like oval or rod-shaped bumps, sometimes resembling bark or buds. They range in color from white, yellow, grey, brown to Horse fly black. These insects can occur on leaves, stems, branches or trunks, and occasionally on fruit. There are two types of scale insects. Soft scales secrete a thin, waxy layer over themselves, which cannot be separated from the insect s body. When you dislodge a soft scale with a pin or sharp pencil point, look for the telltale shiny spot of honeydew. Legs and antennae are attached to the underside of the shell. Because they consume large amounts of plant sap, soft scales excrete a sticky, sugary liquid called Figure 6.11 Members of the Order Hemiptera. Aphids are soft-bodied insects that range in color from green, yellow, red, grey, or black. They suck the juices from leaves and stems causing stunted or deformed buds and flowers, and sometimes curled or puckered leaves. Mealybugs are oval-shaped and covered with a white, woolly coat. They feed on plant sap and exude honeydew. Look for them in the stem crevice and leaf joints. Scale insects are highly destructive pests because they often remain unnoticed until they ve become well-established. They get their name from the protective Mirid Plant Bug Cicada Treehopper Bed bug Mealybug Lygaeid seed bug Scale insects Whitefly Stink bug Aphids Water bug Leafhopper Basic Entomology 139

12 honeydew as a by-product of their feeding. In humid environments the shiny, sticky leaves may be colonized by sooty mold fungi which feed on the honeydew, imparting a black soot-like coating on the leaves. Large patches of sooty mold that blacken leaves and stems are often what draws attention to a scale problem. Armored scales secrete a hard, lacquered covering over their bodies. This cover is not attached and can usually be separated from the scale s body. They typically are smaller than soft scale, about 1 / 16 to 1 / 8 inch in size. Armored scale insects do not excrete honeydew, therefore, do not support the growth of sooty mold. Scale insects produce eggs that hatch into tiny mobile crawlers or nymphs. They move around the plant seeking suitable sites to feed, settle down, secrete their scale covering, and then mature to adulthood. Some species overwinter as eggs beneath the dead female s cover and hatch in the spring; others overwinter as fertilized females and resume feeding in the spring, when they lay eggs and die. Scales are difficult to control. Pick off the adults by hand or with a pair of tweezers. Small populations can be killed with a cotton-tipped swab dipped in rubbing alcohol. Prune out heavily infested limbs. Pesticides are most effective on the crawlers. To detect them, attach a piece of double-sided adhesive tape to a stem above an infested area in early spring before new growth begins. Examine the tape with a magnifying class to identify the specks. There are 1,200 described species of whiteflies that attack a wide array of agronomic, vegetable, and ornamental crops. Their name is derived from the white, powdery wax that is secreted from their abdomen to cover the adult s wings and body. The tiny, white mothlike adults (about 1 / 12 inch long) usually lay between 30 and 500 tiny, white spindle-shaped eggs, usually on the undersides of the leaves of new growth. The creamy yellow eggs turn dark gray after 24 hours. They hatch within 5 to 7 days into inconspicuous, translucent white nymphs called crawlers. The oval, flattened crawlers wander for a short distance before perma- Basic Entomology 140 Figure 6.12 Insects in the Order Hymenoptera. Sawfly Sphecid mud dauber wasp nently settling down to feed. After their first of four molting stages, the nymphs lose their legs and antennae and look like tiny scale insects with a flattened, oval appearance and covered with a waxy secretion. There are three nymphal stages that feed on the plant spaced at two to four-day intervals. The pupal stage lasts about a week. Both adults and nymphs, which are usually found on the undersides of the leaves, suck phloem sap with their piercing and sucking mouthparts. Their feeding results in yellowed or mottled leaves and reduced plant vigor. Leaves may shrivel up and drop prematurely. Similar to aphids, mealybugs, and soft scale insects, whiteflies excrete honeydew as they feed. This sticky sugary solution collects dust and supports the growth of black sooty mold fungi. They produce many generations per year. Hymenoptera: ants, bees, horntails, sawflies, wasps, (Figure 6.12) Adults have two pairs of membranous wings. Larvae have no legs (wasps, bees, ants) or three pairs of legs on thorax and more than four pairs of legs on abdomen (some sawflies). Generally have chewing mouthparts. Rather soft-bodied or slightly hardened-bodied adults. Complete metamorphosis. Many beneficial species prey on or parasitize harmful insects. Isoptera: Termites (Figure 6.13) Social insects that produce colonies comprised of hundreds to thousands of individuals comprising a caste system of workers, soldiers, reproductives, and winged forms known as alates. Chewing mouthparts Simple metamorphosis: egg, an immature, and an adult stage. Ichneumon wasp Braconid wasp Parasitic wasp Cuckoo bee Horntail sawfly Potter wasp Ant

13 Figure 6.13 Comparison of a termite swarmer and a swarming ant. throughout the state. However, Formosan subterranean termites are known to occur mainly in the coastal counties, up to Charleston county. A mature Formosan subterranean termite colony may be comprised of millions of workers in contrast to a native colony that may support several hundred thousand workers. Because of their sheer numbers, Formosan subterranean termites are considered the most destructive termites. Subterranean termites feed on cellulose-containing materials, such as dead trees. They digest wood with the help of microorganisms which live in their digestive tracts. Termites become a problem when wooden structures are built over or near their colonies. They build earthen shelter tubes from the ground into the structure for protection from predators and to help maintain a moist environment. There are two major types of subterranean termites in South Carolina: several species of native subterranean termites and the imported Formosan subterranean termite. Native subterranean termites are common Figure 6.14 Order Lepidoptera. Swallowtail Cabbageworm Fritillary Polyphemus moth Clearwing moth Skipper Sphinx moth Hairstreaks Lepidoptera: butterflies, moths, skippers (Figure 6.14) Adults are soft-bodied with four well-developed membranous wings covered with small scales. Larvae have chewing mouthparts. Adult mouthparts are a coiled, sucking tube. Adults feed on nectar. Larvae or caterpillars are wormlike, variable in color, and voracious feeders. Larvae generally have simple legs on the abdomen as well as the thorax. Complete metamorphosis. Neuroptera: alderflies, antlions, dobsonflies, dusty wings, lacewings, mantidflies, snakeflies (Figure 6.15) Insect predators, both larvae and adults. Many are aquatic. Two pairs of membranous wings. Chewing mouthparts. Complete metamorphosis. Odonata: damselflies, Dragonflies: (Figure 6.16) Insect predators Nymphs are aquatic. Adults feed on mosquitoes, midges, and other small insects. Two pairs of membranous, manyveined wings. Damselflies fold their wings over their backs at rest; dragonflies keep their wings out horizontally. Chewing mouthparts. Simple metamorphosis. Codling moth Orthoptera: crickets, grasshoppers, praying mantids (Figure 6.17) Adults are moderate to large, of- Basic Entomology 141

14 Figure 6.15 Order Neuroptera. Dustywing Snakefly Figure 6.16 Order Odonata Damselfly Figure 6.17 Order Orthoptera Dobsonfly Alderfly Lacewing Dragonfly* ten rather hard-bodied. Simple metamorphosis. Adults usually have two pairs of wings. Forewings are elongate, narrow and hardened; hindwings are membranous with extensive folded area. Chewing mouthparts. Antlion Both adults and nymphs can be damaging. Hind legs of forms other than mantids and walking sticks enlarged for jumping. Mantispid Immature stages are called nymphs and resemble adults but are wingless. Praying mantids are beneficial predators. Thysanoptera: thrips (Figure 6.18) Adults are small, soft-bodied insects. Sucking mouthparts Varied metamorphosis (a mixture of complete and simple). Found on flowers or leaves of plants. Wings in two pairs, slender, featherlike and fringed with hairs. Flower thrips are tiny ( 1 / 16 inch long) yellowish-brown to amber-colored insects that damage rose flowers by rasping the tissues and then sucking up the sap that oozes out. Their feeding causes flower buds to become streaked with brown discolored areas. Often the buds fail to open or the flowers look distorted. Thrips are especially fond of white or light-colored flowers. To check for thrips, open up a suspected flower over a sheet of white paper and look for tiny scurrying insects that resemble slivers of wood. Thrips are difficult to control. Fortunately, they re eaten by minute pirate bugs, ladybugs, lacewings, and big-eyed bugs. Remove and discard any infested flowers. Grasshopper Mole Cricket Katydid Walkingstick Mantid Cricket Common Noninsects A number of insect relatives belong to the Phylum Arthropoda. They include spiders, ticks, and mites (Arachnida), pill bugs (Crustacea), millipedes (Diplopoda), centipedes (Chilopoda). Snails and slugs in the Phylum Mollusca, are also found in the garden and landscape. Arthropods lack the characteristic features Basic Entomology 142

15 Figure 6.18 Thysanoptera Figure 6.19 Class Arachnida. Thrips Spider Mite Tick of insects. Arachnids, for example, have two main body regions: a cephalothorax and an abdomen, eight legs, no antennae, and no wings. Arachnids: mites, spiders, and ticks (Figure 6.19) Arachnids have no antennae, no wings, and two body regions that not are clearly distinct from one another. Adults have four pairs of jointed legs while adult insects have six legs. Spider mites are tiny, soft-bodied arachnids. They are common pests of many fruit and nut trees, vegetable crops, ornamentals, and houseplants. With their piercing mouthparts, spider mites suck plant sap from the undersides of leaves causing the upper surfaces to turn bronze or yellow. Eventually the leaves may turn brown and fall off. Heavily infested leaves can be covered with webs. Common species include southern red or cool weather mites which reproduce rapidly in spring and fall. Twospotted spider mites (pale yellow, green, brown or red) have two spots on their backs; they become active during the heat of summer. Other common species are European red mites, which are red with white spines, and clover mites, which are reddish brown or gray and flat with very long front legs. Many mites are smaller than the period on this page and are best viewed with a magnifying glass. To inspect for mites, simply tap an affected leaf over a piece of white paper and In 2011, parts of South Carolina will experience a major emergence of 13-year periodical cicadas (Magicicada tredecim). Since 1998 the young cicadas have been below ground sucking sap from roots and are expected to emerge in late April and early May. The 13-year cicada is a southern form while the 17-year cicada (M. septendecim) tends to be a northern form. look through the lens for tiny moving specks. Eriophyid mites include rust, bud, and blister mites. They have four legs instead of the usual eight legs--a characteristic of most arachnids. Spiders are larger than mites and have two body regions that are distinct from one another. There are 3,000 species of spiders that live in the U.S. Most are beneficial predators, and many spiders do not produce webs. Instead, they lie in wait for their prey. They feed on insects and other small animals by paralyzing them with venom. Three dangerous spiders are commonly found in South Carolina, all widows. The Southern black widow is found throughout the state. It is easily identifiable by the shiny, black bulbous body with the abdomen bearing a red hourglass marking on its underside. The Southern black widow usually is found outdoors under stones, logs, or other dark protected areas in and around buildings. The Northern black widow is found in the mountains and the Piedmont of South Carolina. The Northern black widow looks similar to the Southern black widow; however, it lacks the hourglass marking on the underside; it has two red mark spots instead. The brown widow, extremely rare in South Carolina, is a widespread species found in tropical areas. It was introduced into Florida and has expanded its range northward into South Carolina. In the late 1990s it had been reported in Charleston and Beaufort. Since the summer of 2002 more reports of its presence have been made in numerous areas of the state. Brown widow spiders are gray to brown in color with white and black markings on the top surface of their bulbous abdomens. The hourglass marking on the underside of the abdomen is yellow to orange and the legs have dark bands. All three widow spiders in South Carolina are shy and will try to flee rather than bite a human. Cases of widow bites occur when a spider is pressed against the skin of a person (for example, when putting on clothes or shoes) or when a hand is reached into dark areas where the spider is present. It has been reported that the venom of the brown Basic Entomology 143

16 widow is as toxic as the black widow spider, but they are less likely to bite and do not defend their webs as vigorously as black widows. The brown recluse spider, extremely rare in South Carolina, is often confused with harmless wolf spiders and other hunting spiders. The spider is light brown or grayish with long, delicate legs. The fiddle or violin outline on the back is not a dependable character since many brown spiders have similar markings. It is about the size of a quarter (with legs) when mature. The primary key to identification are the three pairs of eyes. Ticks are external parasites of people and animals. They need a blood meal to survive and reproduce. Ticks can feed on humans and other mammals, reptiles, birds or even frogs. All life stages of ticks feed on blood. Ticks can transmit several diseases, such as Lyme disease, rocky mountain spotted fever, tick paralysis, and others, but most tick bites do not result in illness. Chilopoda: Centipedes (Figure 6.20) Centipedes strongly resemble millipedes, except that they have longer antennae, are more flattened in cross-section, and have only one pair of legs on each body segment. They are beneficial predators of other arthropods. Centipedes are nocturnal and actively seek dark shelter if exposed. The first pair of legs possess venom glands, which they use to subdue Figure 6.20 Class Chilopoda. their prey. Order Isopoda Sowbugs and pillbugs (Figure 6.21) Sowbugs and pillbugs look similar in appearance. They are gray, oval-shaped, and about 1 / 4 to 5 / 8 inch long. Their hard, rounded outer shell is composed of a number of plates. Sowbugs have two taillike structures, unlike pillbugs. Another difference between the two is that pillbugs or roly-pollies can roll up into a tight ball when disturbed; sowbugs cannot. Sowbugs and pillbugs are active at night, mainly feeding on dead plant material and occasionally, young plants and their roots, often causing little injury. They breathe with gill-like structures and must be in very moist areas to survive. Look for them during the day in moist areas, such as under rocks, boards, mulch, or leaf-litter. They do not bite and are completely harmless to humans. Diplopoda Millipedes (Figure 6.22) Millipedes are wormlike with two visible anatomical regions: a head and body. They are generally round in cross-section, and all but the first four or five body segments possess two pairs of legs. Millipedes are generally inoffensive creatures that feed on fungus and decaying plant material. At times, they can be fairly destructive to vegetables or other plants in greenhouses. Centipedes Figure 6.22 Class Diplopoda. Figure 6.21 Order Isopoda. Millipedes Sowbug Basic Entomology 144

17 Identifying Insects Entomologists examine insects under a magnifying lens, dissecting scope, or microscope and use anatomical features or body parts to distinguish, classify, and identify insects. Identifying insects to the species level is often difficult, and may require a key. There are field keys that help identify the insect based on plant damage, such as insects that mine or eat holes in the leaves as opposed to sap-sucking insects that cause discolored or deformed leaves. When an insect specimen is available, keys help identify the insect from orders down to the species level. Identifying a given insect to the species level is often difficult. It may include counting the number of teeth on the mandibles or the number of segments on the antennae. Sometimes entomologists use the arrangement and length of hairs on the head, thorax or abdomen or the arrangement of veins in the wings as identifying characteristics. For home gardeners, knowing the exact species of an insect may not be necessary, especially after you determined that it s beneficial or harmful. If it s a harmful pest, such as aphids, the exact species does not have to be determined. After all, the control measures for most aphids would be the same, regardless of the species. The same could be said about mealybugs, most soft scales, spider mites, and many other common pests, provided that you identified the host plant. Knowing the identity of the host plant is very important because it helps to reveal an insect s identity. Although some insect pests are general feeders that feed on a variety of different plants, many are quite host-specific. For example, the dogwood twig girdler only attacks dogwood. You will not find it feeding on pines, oaks, camellias, or other plants. Knowing the identity of the host and pest is also important, when providing recommendations for chemical pesticides, particularly on vegetables, fruit, or other edible crops. Phylum Mollusca: Snails and slugs Snails and slugs are small soft-bodied animals They are not arthropods, but they can be troublesome pests in the garden. The brown garden snail (Helix aspersa) and the gray garden slug (Deroceras reticulatum) are among the most bothersome pests in South Carolina. They are very similar to each other except snails have hard shells and slugs do not. They can cause serious damage in the garden, and often remain unseen, since they feed at night or on rainy days. During the day they can be found hiding in damp places such as in thick groundcovers or under flower pots. The most characteristic signs of their presence are the trails of mucus they leave wherever they crawl. Slug Snail Credit: California Master Gardener Handbook Dennis R. Pittenger, ed. Univ. of Calif. Agric. and Natural Resources, Pub Copyrighted by the Regents of the Univ. of California and used with permission. Snails and slugs feed on both decaying and living plant material. Parts of plants that can be affected include leaves, stems and below-ground parts. They produce large, ragged holes and can completely consume young seedlings. Juveniles and adults feed on a wide range of edible and ornamental plants. They are especially troublesome on hostas, strawberries, lettuce and cabbage. Young plants are especially vulnerable to attack. Silvery slime trails and irregularly shaped holes in the leaves are the most characteristic signs of slugs. Most of the damage occurs close to the ground. A close inspection of plants at night, early in the morning, or on cloudy, wet days is the best way to catch slugs feeding. Where slugs can be handpicked, they can be dropped into soapy water. Setting out an inverted clay pot, board, or grapefruit rind near favorite plants will give the slugs a place to congregate. Pitfall traps baited with beer or a simple mix of sugar water and yeast will attract and drown slugs, although these must be filled and emptied regularly. Their protective layer of slime makes many physical barriers ineffective, although bands of wood ashes and diatomaceous earth have proven useful. More effective are strips of copper foil or even copper screen attached to the edges of pots, raised beds, and tree trunks. Finally, since slugs prefer moist conditions, eliminating trash and other debris in the garden, limiting irrigation, and delaying mulching until seedlings have grown larger will all reduce problems with slugs. Basic Entomology 145

18 Submitting Insect Samples for Identification The identification of an insect or related pest is the first step in determining whether it should be controlled and in obtaining recommended control measures. Clemson University provides identification assistance when it is needed. A good specimen and supporting information are essential for pests to be correctly identified. County Extension offices furnish information on what is necessary for collecting, preserving, and shipping specimens and the supporting information that should be included. The county offices can submit samples for you. If you decide to submit samples on your own, there are several steps you should take. Preserving and Packaging In general, most insects should be preserved immediately after collection. Several specimens should be included if possible. Most specimens can be killed and preserved in glass or plastic jars containing 70 to 90-percent ethyl or isopropyl (rubbing) alcohol. Do not send insects in water. Large, fragile insects such as butterflies and moths should be killed in a freezer and stored in a crush proof container without alcohol. Tissue paper gently placed around the specimens will keep them from being damaged in the mail. Pests on plants such as mites, thrips, aphids, scale, and other very fragile insects should be sent in on the diseased plant. These insects are easily damaged by removal from the plant, and their appearance on the plant as well as damage symptoms may be very important for accurate identification. Small caterpillars, grubs, and maggots should be sent live in a plastic bag with some of the host material, if possible. It may be necessary to rear some of these to the adult stage for positive identification. Place the plastic bag in a container that will not be crushed in the mail. Other types of insects can be kept alive if they are placed in a small, loosely capped container with a slightly moistened paper towel or a cotton swab moistened with a drop of water. The following information should be included for each sample submitted: Name of collector. County and nearest town. Date collected. Where found, such as host plant, animal, or location in a building. If the host was a plant or animal, give the stage of growth. If the specimen was found on a person, provide the person s name and phone number. Degree of infestation (heavy, medium, light) and type of damage. Insecticide used for control and results if appropriate. It is becoming more common for individuals with digital cameras to send images of specimens by . This can greatly speed the process of determining the type of specimen and the appropriate control measures if needed. However, identification of insects and related arthropods from electronic images can be challenging. Being three-dimensional, many important characters used to identify insects can be out of focus in an image with limited depth of field. For example, the number of parts on the antennae, placement of hairs and spines on the body, shape of the mouthparts and the number and shape of veins in the wings may all be needed to key an insect to species. It may not be possible to capture all the necessary key characters to fully identify a pest. Fortunately in some situations, the species of a pest may not be necessary to make an appropriate control recommendation. Before imaging an insect or related arthropod for identification, you should determine the level of identification you feel you need. For example, when concerned about a specific species such as a brown recluse spider or Formosan termite, it may be more efficient to mail the sample by the traditional process so detailed identification can be made. In addition, you will probably need to mail small arthropods such as mites, larval ticks and minute flies. For more general identifications, large specimens or identifications with pressing time constraints such as structural pests delaying a home sale, digital images may work well. The following guidelines are designed to help you make decisions about imaging insects, related arthropods and the damage they cause. Whenever possible, lay a simple ruler or a common item such as a penny next to the specimen so the relative size of the creature can be determined. When possible, take an image of damage nests. Photograph damage where it interfaces with normal plant tissue, lumber, food products, etc. Use a contrasting background color to the specimen. If in doubt, use a light gray background. Use an intensity of light that best depicts the accurate color of the specimen. When many pests are present, take an image of several specimens in one frame. Attempt to select the best preserved specimen to provide a close-up image of entire top, bottom and head. When imaging the head, try to get the base of the antennae, eyes and mouth in focus. For specimens flattened side-to-side, such as fleas, a view will be needed. Electronic Images Reprinted from Submitting Insect Samples for Identification (IIS/HS-22, E. P. Benson and C. S. Gorsuch). Basic Entomology 146

19 Diagnosing Plant Problems Caused by Insects and Mites Determining the cause of poor plant performance is a difficult task because Master Gardeners and other diagnosticians often have incomplete evidence. The diagnostic process involves gathering the facts from the Plant Problem Clinic Diagnostic form and from the person submitting the sample. Then you need to draw on your past experiences, published references, and other resources. Ideally, a diagnosis should include a site visit which yields more evidence to help with an accurate diagnosis. Unfortunately, visiting the location where the sample was taken is often not possible. So, it s important that when confronted by a problem, the Master Gardener follows these tips for diagnosing insect and mite-related problems: Know the identity of the afflicted plant to determine the identity of the pest which results in successfully managing it. A majority of insects and mites have preferred host plants, while some are general feeders. Most of the references are organized by host plants that are being attacked which will help you determine the insects that could be involved. Is the problem localized to one or several plants? Is it on a single species or several species of plant? What type of damage is occurring? When people notice a pest problem and seek advice, it may be too late to take any corrective action in that particular growing season. In some situations, the pest may be gone and the damage remains. Become familiar with the pest s life cycle to determine if there are subsequent generations that need to be controlled. Exercise caution before making a recommendation based on the client s verbal description. Ideally, see the damage and the insect itself to avoid making an inaccurate identification. Use a hand lens, if necessary. Your client may have to resubmit digital images of the pest according to the guidelines listed in the box on the left. The incorrect identification of an insect results in ineffective control measures, unnecessary expense, and potential harm to beneficial insects. Master Gardeners represent Clemson University. Make your diagnosis or give research-based recommendations that have been verified by Clemson University specialists. Consult the resources at the end of this chapter. Present all appropriate options--handpicking, biological, chemical--to your clients and allow them to choose the best method or combination that best suits their needs. Do not be afraid to say, I don t know. When in doubt, do not make a diagnosis. Refer to your county agent, specialist, or Plant Problem Clinic. Be aware that the problem may be attributable to other causes other than insects or mites, such as disease, improper cultural practices or conditions that include too much or too little water, poor drainage, low or high light levels, physical or chemical injury, not adapted to the location, too high or too low temperatures, and excessive or deficient levels of nutrients. Refer to Chapter 19, Diagnostic Key to Landscape Plant Problems, for a broader perspective on diagnosing plant problems. In addition, read the Master Gardener logs where questions and answers are recorded to familiarize yourself with the seasonal problems. Also, study known samples that have been identified by a county agent, specialist, or Plant Problem Clinic. Basic Approaches for Successfully Managing Pest Insects Identify the Problem. People have different tolerance levels regarding pest infestations. Some will be indifferent about the number of aphids on their shrub roses, while others who show roses may want to take action when aphids first appear. In some cases when a problem is brought to a Master Gardener s attention, it s too late too take any action because the damage is already done. When orange-striped oakworms have defoliated oak trees in September, it s too late to control the pest. Killing mature or pupating caterpillars to reduce the severity of next year s infestation is not an environmentally sound approach. Besides, the oaks will shed any remaining leaves in the next few months, so control is not warranted this late in the season. Solving an insect pest problem entails more thought and knowledge than just identifying the pest. Select a Proper Management Strategy. Select one or a combination of appropriate methods that insure the safety of the people involved as well as the environment. If several methods are available, suggest all that are reasonable and approved by Basic Entomology 147

20 Clemson University. Take into account proper timing of the application which coincides with the most vulnerable time in the life cycle of the insect. Then, allow your client to choose the approach that s best for them. Because of their toxic nature, special attention should be devoted to pesticides to ensure their proper use. Pesticides must be used in strict accordance with the label instructions. The ornamental or food crop must be listed on the label or referred to under a general heading such as lawns, shrubs, trees, or other ornamentals. Products may have identical ingredients and are sold by different manufacturers, but their formulations, pests controlled, and application sites may vary. The user is responsible for finding a product that is appropriate for the particular pest, plant, and site. See Chapter 9 for information on pesticide formulations, labels and labelling, application equipment, sprayer calibration, storage and disposal, and environmental concerns. Evaluate the Results. Evaluate the pest control results to avoid or effectively manage this pest The brown Carolina Mantid (Stagomantis carolina) (Insect Order: Mantodea, Family: Mantidae) became the state insect of South Carolina in problem in the future. It may mean planting squash in early spring to escape squash vine borer or replacing Japanese euonymus (Euonymus japonicus) with more resistant species to avoid having to protect it from euonymus scale. Benefits and Value of Insects Insects must be studied carefully to distinguish the beneficial from the harmful. People have often gone to great trouble and expense to destroy insects, only to learn later that they were not only harmless but were actually saving crops by eating destructive insects. Insects are beneficial to gardeners for the following reasons: Insects are pollinators. Most common fruits, melons, squash, and many other vegetables, and many ornamental plants (chrysanthemums, irises, orchids, and yuccas) are pollinated by insects. Parasitic predatory insects destroy harmful insects. Figure 6.23 Commonly occurring beneficial insects in gardens and landscapes. Assassin bug Trichogramma wasp Predaceous stink bug Damsel bug Green lacewing Basic Entomology 148