Tricks for generating lift: I. A surface, with support II. Some sort of articulation mechanism III. Muscles to power the surface (more later) IV. Mechanisms to generate lift Passive mechanisms Tilt Twist Camber Active mechanisms Path of wing tip Fast-flying birds (from side & top): III II I III & IV co-opted from leg base Slow-flying birds (side & top): Complex wing motion (active & passive mechanisms) Drosophila (Diptera) Odonata: Anisoptera Muscidae (Diptera): red = top surface, blue = bottom surface 1
Tracing the path of wing motion in Hymenoptera backwards flight forward flight Compare with hovering flight in a bird: hovering flight Changes in orientation of body axis changes in flight body axis Ephemeroptera Plecoptera Plecoptera Sialidae = path of fore wing = path of hind wing Mecoptera Hemerobiidae Sisyridae Trichoptera Symphyta Fulgoroidea Muscidae Coleoptera 2
Clap & fling (also clap & peel, etc.) Closing dorsally (upstroke) leading edge of wing (clap) 1 2 3 4 anterior posterior axial view Opening dorsally (downstroke) leading edge of wing (peel) 1 2 3 4 anterior posterior axial view Major wing regions: Remigium, Vannus/Anal area/clavus, and Jugum a = axis of rotation (torsion) b = axis of mass c = axis of aerodynamic pressure area of articulation pterostigma Jugum Vannus Remigium anal suture Ground Plan of insect wing: relatively large size isopterous in structure & venation half as broad as long smooth membrane: semi-transparent, little pigmentation, and a few small hairs on veins complete complement of veins 3
Changes in the proportions of remigium vs. vannus Generalized condition: archaic Insecta area of articulation jugal area (jugum) anal area remigium anal suture (also called vannus or clavus) Orthoptera: Acrididae remigium anal area Coleoptera: Staphilinidae remig. anal area (fan) folds of fan anal area (fan) lines of axial folding Front wing/back wing differences: size & texture elytron Coleoptera anal fan Blattodea coriaceous texture Hemiptera: Heteroptera membrane coriaceous anal fan (vannus) Orthoptera hemelytron 4
Other color & textural changes: hairs (setae) and scales Colors: aposematic thermoregulation crypsis & mimicry courtship & mating Trichoptera Lepidoptera Hairs & scales: protection smoothing of air flow sensing air movements Dermaptera elytron Front wing/ back wing differences: extreme specialization haltere Diptera resilin 5
Neuroptera: Nemopteridae More front wing/ back wing differences: Tails Lepidoptera: Papilionidae Likely function: protection by predator distraction Front/back, left/right, & sex differences: strigils left right male (left = right) female female male 6
Jugal specializations and wing coupling mechanisms by a jugum: Hepialidae by a frenulum: Psychidae (ventral views) jugum frenulum radial vein by hamuli: Hymenoptera retinaculum hamulus humeral lobe Wing coupling mechanisms, magnified Frenulum in aganaid moth retinaculum frenulum (classified as frenate moths ) Hamuli in wasps 7
Odonata: Anisoptera Pterostigmata Hemiptera: Aphidae Neuroptera: Ascalaphidae pterostigma Functions: flexible tip for aerodynamics flexible tip for clap & peel fluid-filled counterweight to prevent stalling other unknown advantages Independently evolved many times Insect wing venation: ancestral archedictyon (an ancient net ) 8
Importance of wing venation for classification & phylogenetic analysis: 1. Single origin of wings: interpretations can be based on the assumption of monophyly & real homology 2. Conservative evolution: venation changes slowly so phylogenetic signal remains intact over long time periods 3. Provides a set of characters shared by nearly all insects 4. Nicely preserved in the fossil record -- often, only wings are present (like leaves of extinct plants) Interpreting wing venation in modern insects Major wing veins: Costa (C) (+) Subcosta (Sc) ( ) Radius (R) (+) Radial Sector (Rs) ( ) Anterior Media (MA) (+) Posterior Media (MP) ( ) Anterior Cubitus (CuA) (+) Posterior Cubitus (CuP) ( ) Anal (A) (+) R+ M- Interpreters: Cu+ - Redtenbacher - Hagen (mid-1800s) - Comstock & Needham (1918 book) 3A+ C+ Sc- R+ Rs- MA+ MP- CuA+ CuP- 1A+ 2A+ CONVEXITY (+) CONCAVITY ( ) Sc 1 Sc2 R 1Rs1 Rs 2 Rs 3 Rs 4 MA 1 MA 2 MP 1 MP 2 MP 3 MP 4 CuA2CuA1 9
A more detailed view of wing venation axillary sclerites pterostigma Major wing veins: Costa (C) Subcosta (Sc) Radius (R) Radial Sector (Rs) Anterior Media (MA) Posterior Media (MP) Anterior Cubitus (CuA) Posterior Cubitus (CuP) Anal (A) Homologizing wing veins: the pretracheation theory A B B WING RADIUS Rs C Sc cross-over R John Henry Comstock 1A Rs+CuA (Cu 1 ) C Sc R Rs r s M 1 MA (+) RADIUS (+) Rs (-) 3A 2A 1A M 2 Cu2 Cu 1 Comstock & Needham; Cornell (U.S.) school of venation. 10
Alternatives to the pretracheation theory ( European school of wing venation Tillyard, esp.) Tracheae grow into pre-existing lacunae (Holdsworth 1937) cuticular surfaces Robin John Tillyard tracheal branch lacuna nerve Homologizing wing veins: Convexities and concavities (Martynov & Lameer, 1930s) convex veins C(+) R(+) MA(+) CuA(+) 1A(+) concave veins Sc( ) Rs( ) MP( ) Exceptions (too specialized, or flattened): tegmina & elytra mid-section of holometabolous wing CuP( ) cuticular layers (separation using KOH -- Holdsworth s method) Proliferation: Neuroptera: Chrysopidae cross-vein marginal twigging Hymenoptera: Chalcidoidea Reduction: one vein Odonata: Anisoptera Special functions: nodus arculus Thysanoptera one vein setae pterostigma Coleoptera elytron Hemiptera: Heteroptera hemelytron 11