Dermestid Beetles: A Self-Tutorial for PPQ Identifiers (Part 2) Charles F. Brodel, Ph.D. Collateral National Coleoptera Specialist USDA APHIS - PPQ Miami Inspection Station Miami, Florida August, 2008
Tutorial Contents Larvae Dermestidae: Taxonomic characters Frequently intercepted genera: Taxonomic characters Trogoderma granarium: Taxonomic characters Preparing Slides of Labrum-Epipharynx Molecular Diagnostics Acknowledgment References 2
Larvae 3
Dermestidae: Taxonomic Characters 4
Sclerotized tergal plates on dorsum 5
Bands, clusters, or tufts of long and short setae/scales of various types 6
Frequently Intercepted Dermestid Genera: Taxonomic Characters 7
All identifications of the 4 most frequently intercepted genera should be made based on a combination of: Multiple characters Knowledge of host material or circumstances of detection, as described under Feeding Habits in Part 1 Reference specimens or digital images, if available 8
Taxonomic keys are available for frequently intercepted domestic genera as well as other seldom-intercepted genera. Consult Beal, R. S. (1991): Nearctic region Rees, B. E. (1943): Nearctic region 9
Anthrenus 10
Body with hastisetae 11
Abdominal tergal plates 5 6 sinuate laterally Dorsal view: Hastisetal tufts removed from tergites 5 and 6; posterior margin of tergite 4 evenly rounded Lateral view of tergites 5 and 6; hastisetal tufts present 12
Hastisetae attached to membranous area behind tergal plates 5, 6, 7 Arrows indicate that tufts originate beneath posterior margin of tergal plate 5 13
Setal tufts tight and almost overlapping in medial area 14
Attagenus 15
Body without hastisetae 16
Body setae usually slender and pointed 17
Dermestes 18
Pair of horn-like processes (=urogomphi) on next-to-last abdominal segment NOTE: Urogomphi are much smaller on early-instar larvae 19
Trogoderma 20
Body with hastisetae 21
Tergal plates 5 7 straight or evenly curved Hastisetal tufts removed from one side of tergal plates 6 and 7 22
Hastisetae attached toward posterior margin of tergal plates 6-8 Dotted lines indicate posterior margins of tergal plates; arrows indicate attachment points for hastisetal shafts 23
Setal tufts spread out at ends and not tending to cross each other at median 24
Trogoderma granarium: Taxonomic characters 25
Epipharynx with 4 sensory papillae, usually in single sensory cup slide 1 Trogoderma granarium + T. glabrum: enlarged image of sensory cup at lower right; infrequently, 4 sensory papillae occur in 3 separate cups of 2, 1, and 1 26
Epipharynx with 4 sensory papillae, usually in single sensory cup slide 2 Species of Trogoderma other than granarium and glabrum have 6 papillae in sensory cup; enlarged image of sensory cup at lower right; infrequently, papillae occur in separate cups of 4 and 2 or 2, 2, 1, and 1 27
Antecostal suture on 8 th abdominal segment almost always absent, that on 7 th faint, interrupted -- slide 1 To observe sutures, first clear tufts of hastisetae from last 2 or 3 tergal plates CAUTION: Do not confuse anterior margin of sclerotized tergal plate with antecostal suture. Suture lies posterior to this margin. 28
Antecostal suture on 8 th abdominal segment almost always absent, that on 7 th faint, interrupted -- slide 2 Trogoderma granarium (fully distended) + sometimes T. ornatum; NOTE: if suture present, then faint and usually broken Trogoderma sp., fully distended **** Arrows point to antecostal sutures (= transverse lines)**** 29
Setae on antennal segment 1 reach to apex of segment 2 or beyond Trogoderma granarium: Setae shown at left on segment 1 reach beyond apex of segment 2 T. variabile and others: setae shown at left on segment 1 do not reach apex of segment 2 30
Setae originate on about two thirds or more of circumference of antennal segment 1 Trogoderma granarium: setae arise from about two thirds of circumference of antennal segment 1 Trogoderma variabile and others: setae arise primarily on mesal side of antennal segment 1 and occupy about a third to a half of circumference 31
Preparing Slides of Labrum-Epipharynx 32
Head capsule ventral view NOTE: Objective is to sever labrum-epipharynx from clypeus 33
STEPS Observe antennal characters while specimen in alcohol: 1. Whether some antennal setae on segment 1 extend at least to apex of segment 2 2. Whether setae are restricted to mesal side of antenna or occupy perhaps two-thirds of the circumference; a dorsal view of antenna is best for this determination ** NOTE: Antennal segments must be fully extended for observations to be valid. Perform the following steps on a stereoscope stage. While holding down specimen with a pin, pry away mandibles with a needle or pin, sever maxillolabial complex, and fold labrum downward so that its underside is face up on watchglass. Turn watchglass so that specimen and labrum face to the right (for right-handed individual). Use scalpel microtool to sever labrum from clypeus, usually with one or two north-south strokes. 34
Use lifter microtool to transfer labrum-epipharynx from watchglass to small drop of Hoyer s medium on a small-diameter, circular cover slip. Less Hoyer s is better than more. Arrange labrum-epipharynx so that underside is facing downward. Lower a microscope slide onto the cover slip and then turn it over. Exert pressure with a wooden or plastic tool handle directly atop the specimen. The objective is to get the surface of the labrum-epipharynx as parallel as possible with the glass surface so that sensory papillae will be in one focal plane under a compound microscope. Too much Hoyer s allows labrumepipharynx to float and end up at an angle to the glass slide, or even to turn over. Heat in oven at 40 C for 5-15 minutes. View under compound microscope at 400X or more. Phase contrast microscopy assists viewing. Focus upward from the surface of the epipharynx to see the distal sensory cup with papillae (seen as tiny dots in a circle). 35
Head capsule ventral view Mandibles and maxillolabial complex excised from capsule Labrum-epipharynx pushed downward from left to right, to a somewhat level position Labrum-epipharynx severed from clypeus 36
Labrum-epipharynx placed atop a drop of Hoyer s medium on a 15-mm-diameter cover slip (above); shown after being positioned ventral side down (right) 37
Molecular Diagnostics Some specimens of Trogoderma submitted for identification have confusing sets of morphological characters, perhaps due to hybridization between populations. A study using enzyme-linked immunosorbant assay (ELISA) (Stuart et al. 1994) demonstrated differentiation among 6 U.S. species of Trogoderma. Another study using random amplified polymorphic DNApolymerase chain reaction (RAPD-PCR) separated 4 pest species from 19 native species of Trogoderma in Australia (Emery et al., Internet). Work to achieve similar results has begun using mitochondrial DNA markers in Australia (M. Castalanelli). It is hoped that kits will someday be developed to separate species of Trogoderma regardless of variability within populations, stage of development, sex, body part, and age. 38
Acknowledgment I am grateful to Alan Barak, USDA-APHIS- PPQ-CPHST, for supplying many of the specimens from which digital images were produced. 39
References Armitage, H. M., G. T. Okamura, and F. L. Blanc. Undated. Illustrated key to species of Trogoderma and to related genera of Dermestidae commonly encountered in stored grain in California. California Department of Agriculture. 5 pp. Banks, H. J. 1994. Illustrated identification keys for Trogoderma granarium, T. glabrum, T. inclusum and T. variabile (Coleoptera: Dermestidae) and other Trogoderma associated with stored products. CSIRO Australian Division of Entomology Technical Paper No. 32. 66 pp. Beal, R. S., Jr. 1954. Biology and taxonomy of the Nearctic species of Trogoderma (Coleoptera: Dermestidae). University of California Publications in Entomology 10(2): 35-102. Beal, R. S., Jr. 1956. Synopsis of the economic species of Trogoderma occurring in the United States with description of a new species. Annals of the Entomological Society of America 49: 559-566. 40
Beal, R. S., Jr. 1960. Descriptions, biology, and notes on the identification of some Trogoderma larvae (Coleoptera, Dermestidae). Agricultural Research Service, USDA Technical Bulletin No. 1228. 26 pp. Beal, R. S. 1991. Dermestidae (Bostrichoidea) (including Thorictidae, Thylodriidae), pp. 434-439. In Stehr, F. W. (ed.) Immature Insects, vol. 2. Kendall/Hunt Publishing Co., Dubuque, Iowa. Beal, R. S. 2003. Annotated checklist of Nearctic Dermestidae with revised key to the genera. The Coleopterists Bulletin 57(4): 391-404. Emery, R., I. Dadour, S. Lachberg, A. Szito, and J. Morrell. Undated. The biology and identification of native and pest Trogoderma species. Grains Research and Development Corporation Project No. DAW 370. http://agspsrv34.agric.wa.gov.au/ento/trogo/trogo%20final%20r eport.htm#_toc439060849 41
Hava, J. 2004. World keys to the genera and subgenera of Dermestidae (Coleoptera), with descriptions, nomenclature and distributional records. Acta Musei Nationalis Pragae, Series B, Natural History 60(3-4): 149-164. Herrmann, A. and J. Hava. 2005. A contribution to the genus Phradonoma Jacquelin du Val, 1859 from South Africa (Coleoptera: Dermestidae: Megatomini). Genus 16: 183-191. International Plant Protection Committee. (unpublished). International standards for phytosanitary measures. Annex to ISPM No. 27 (Diagnostic protocols for regulated pests) Trogoderma granarium. 26 pp. Kingsolver, J. M. Undated. Notes on the pictorial key for identification of the larvae of dermestid genera. Cooperative Economic Insect Report 13(15): 4-12-63. 42
Kingsolver, J. M. 1991. Dermestid beetles (Dermestidae, Coleoptera) In Gorham, J. R. (ed.) Insect and Mite Pests in Food. An Illustrated Key. USDA, ARS and USDHHS, PHS, Agriculture Handbook No. 655, Washington, DC, vol. 1: 115-136. Kingsolver, J. M. 2002. 68. Dermestidae Gyllenhal 1808, pp. 228-232. In Arnett, R. H., Jr., M. C. Thomas, P. E. Skelley and J. H. Frank (eds.) American Beetles, vol. 2. Polyphaga: Scarabaeoidea through Curculionoidea. CRC Press, Washington. Matveeva, V. I. 2001. [Identification of the Khapra beetle.] Zashchita I Karantin Rastenii 4:31. (in Russian) Okamura, G. T. Undated. A supplemental character for separating adult Trogoderma granarium Everts, khapra beetle, from other Nearctic Trogoderma species. Cooperative Economic Insect Report 16(9): 147. 43
Rees, B. E. 1943. Classification of the Dermestidae (larder, hide, and carpet beetles) based on larval characters, with a key to the North American genera. U.S. Department of Agriculture Miscellaneous Publication No. 511, Washington, DC. 18 pp. Stuart, M. K., A. V. Barak, and W. E. Burkholder. 1994. Immunological identification of Trogoderma granarium Everts (Coleoptera: Dermestidae). Journal of Stored Products Research 30(1): 9-16. Stibick, J. 2007. New Pest Response Guidelines: Khapra Beetle. USDA APHIS PPQ Emergency and Domestic Programs, Riverdale, Maryland. [http://www.aphis.usda.gov/import_export/plants/ppq_manuals. shtml] 44