Erin M. Biggs1
and Anthony I. Cognato1*
Many species of Dermestidae (Coleoptera) are common scavengers of proteinaceous materials and are economically important pests. Here we provide a checklist and dichotomous key for 45 species of dermestid beetles that are pests in Canada and/or the United States. The key is richly illustrated with photographs, and each species page includes a morphological summary, economic importance, and distribution in Canada and the United States.
Dermestid beetles are well known for their ability to infest a wide variety of stored products and materials of animal and vegetable origin (Bayer et al. 1972; Beal 1961, 1970, 1998; Bousquet 1990; Hinton 1945; Kadej et al. 2013; Rees 1943; Veer et al. 1991). Larvae feed on dried fish and meats, cheese, dried milk, dried blood, bones, skins and hides, hair, furs, feathers, carpets, wool, silk, cereal products, seeds, some grains, and dead insects (Hinton 1945). The larvae cause the majority of the damage while most adults feed on nectar and pollen (Bayer et al. 1972; Bousquet 1990; Hinton 1945; Rees 1943). Both the larvae and adults of Dermestes Linnaeus and Thylodrias Motschulsky can damage commodities, but the adult feeding is less significant (Bousquet 1990; Hinton 1945). In nature, many dermestid species can be found as scavengers in the nests of other insects, arthropods, birds, and small mammals (Beal 1954a, 1961, 1970; Hinton 1945; Kingsolver 2002).
Dermestid larvae are densely covered with long or short spinulate setae, which is one of many characters that most obviously separates the family from other beetles (Rees 1943). The unique appearance or habits of some genera provide diagnostic characters. Dermestes is distinguished from most other genera by their large size and absence of a median ocellus (Hinton 1945). Mature larvae of this genus bore into materials like wood, cork, cotton, mortar, lead, books, plaster, and vegetable fiber to pupate (Hinton 1945). A scale-covered body and deep antennal cavities distinguish Anthrenus Geoffroy (Beal 1998; Hinton 1945). Thorictodes Reitter is relatively minute and lacks compound eyes (Beal 1961, 2003). A single species represents Thylodrias whose adults do not resemble other dermestids because the males have seven externally visible sternites and the females are wingless and larviform (Beal 2003; Bousquet 1990; Hinton 1945). The presence of a single median ocellus and general appearance of the larvae are the main characters that relate this genus to other members of Dermestidae (Hinton 1945; Mertins 1981). Identification to species level typically requires examination of antennae, setae, and some cases the genitalia.
Dermestidae consists of 66 genera and 1,648 valid worldwide species and subspecies, with approximately 192 species recorded from North America (Háva 2018); both species counts have increased by roughly 10 percent, since Háva (2018) as reported by Háva and Herrmann (2021). Most available Nearctic Dermestidae keys concern taxa of a genus or tribe. Few have been published in the last 20 years. Keys to stored-product pests often include other insect families and only the most common dermestid pests (Bousquet 1990). Thus, an updated and more comprehensive key of species of pest dermestids would aid in their identification. Following the nomenclature of Háva's (2015) catalogue of Dermestidae, this key includes 45 economically significant species found in the United States and Canada based on Beal's ratings of pest status of each species (Beal 2003). We included species only occasionally reported as pests as well as notorious pest species. The intent of this key is to provide pest managers and diagnosticians with a tool for identifying the potential source of a dermestid infestation in an indoor environment. Occasionally, species that occur in the wild may be found indoors and these species are discussed in the species pages of morphologically similar species.
Our key is based on morphological features of adults. A key for larval identification was not included because infestations may not be known until adults appear in pest monitoring traps or are found at windows or indoor lights (Robinson 2005) and it is very difficult to use dermestid larvae for species determination (Kadej et al. 2013). A key to the genera of dermestid larvae can be found in Volume 2 of Stehr's Immature Insects (Beal 1991). Photos of male genitalia were not included given that these are not easily observed, but the taxon pages include links to AH's website (dermestidae.com) where photos of male genitalia are available for most species in this key.
The keys of Beal (1956, 1970, 1998, 2003), Bousquet (1990), Casey (1900), Halstead (1981), Hinton (1945), Kadej and Háva (2016), and Kingsolver (2002) were modified to create this key. Beal (2003) and Kingsolver (2002) guided the first eight couplets for the key to genera. The subsequent couplets were similarly arranged. Couplets 12 and 16 were written using diagnostic characters from Hinton (1945). A portion of couplet 43 was written based on the description of Trogoderma anthrenoides (Sharp) (being now a synonym of T. serraticorne) from Beal (1961). In couplet 27 the subspecies of Attagenus unicolor (Brahm) are not distinguished since their habits do not differ, but they are separated in the taxon pages because of the species' significant pest status. Subspecies for other species are listed on the species page but not diagnosed. Information included in the species pages was also gleaned from the above literature.
For some couplets, male or female specimens better facilitate species identification. Females often have more antennal club segments as compared to the males and for some genera the arrangement of setae is often a secondary sexual character (e.g., Dermestes). However, there are exceptions to these observations even within genera (e.g., male Anthrenus museorum have more antennal club segments than females, whereas the clubs of the two sexes in A. verbasci are the same). Observation of the genitalia is the best determination of the sex.
Approximately 500 specimens were examined from the Texas A&M University Insect Collection (TAMU, College Station, Texas), the Field Museum of Natural History Collection of Insects, Arachnids, and Myriapods (FMNH, Chicago, Illinois), the A.J. Cook Arthropod Research Collection (MSUC, East Lansing, Michigan), the Santa Barbara Museum of Natural History (SBMNH, Santa Barbara, California), the University of Alaska Museum Insect Collection (UAM, Fairbanks, AK) and the collection of Andreas Herrmann.
Specimens were photographed using a Canon EOS 5D Mark II with a MP-E 65 mm lens mounted on a Stackshot rail. Images were taken using Zerene Stacker (version 1.04) and EOS Utility (version 220.127.116.11), processed using Helicon Focus (version 7.6.1 Pro), and edited using Adobe Photoshop (version 21.0.1).
Measurements were made at the greatest lengths (parallel to the body axis) the of the body parts.
We reviewed 45 economic important dermestid species among 10 genera that occur in Canada and the US (Table 1). Specimens of each species were examined. We distilled diagnostic characters from several previously published identification keys with the addition of new key couplets to produce a comprehensive key to these 45 species (see Materials and Methods for details). The resulting dichotomous key is illustrated with photographs of each species and diagnostic characters. A glossary is provided to assist with special terminology (Table 2). Species pages follow terminal couplets and provide further morphological diagnosis, description, distribution records, and economic and/or ecological information.
Specific preparation of dermestid specimens facilitates the identification of species (Fig. 1). It is best to 1) soften the specimen in a warm aqueous solution containing pepsin or another protein digestive chemical for several days to a week, 2) remove abdomen and extract the genitalia, 3) rinse the body and abdomen in 100% ethanol, gently blot dry, 4) glue the specimen by the sternum on a glue board (Aufklebeplättchen), 5) stretch the antenna straight, 6) glue the abdomen ventral side up behind the beetle, 7) place the genitalia in a drop of glycerine to manually remove remaining tissue, 8) embed genitalia in a mixture of 50% water, 40% Polyvinylpyrrolidon (PVP), 5% glycerine, 5% sorbitol behind the beetle. For all genera position the genitalia in a ventral view except for Dermestes, which should have their parameres removed and the median lobe of the aedeagus placed in a lateral view
Most species can be diagnosed with the characters provided in the key and species pages. However, there are morphologically similar species that rarely occur indoors and are of unknown pest status. These species are listed on the species pages were applicable. Trogoderma species in the key are the most challenging to identify given their similarity to each other and to other non-pestiferous species including: T. angustum (Solier, 1849), T. ballfinchae Beal, 1954, T. cavum Beal, 1982, T. celatum Sharp, 1902, T. fasciferum Blatchley, 1914, T. mexicanum Reitter, 1881, and T. okumurai Beal, 1964. Dissection of their genitalia as well as of their inner abdominal sternites is often needed to confirm species identity. Provinces/states were not given for species that have broad distributions. New distribution records at the province/state level were not discovered among the examined specimens. This key is limited to species known to be pests in human environments plus a few potential pest species, and therefore cannot be used to identify all dermestid species or genera known from Canada and the United States. If in doubt of an identification, please seek advice from taxonomic experts such as, AH and Jiri Háva. In addition, citation of taxonomic identification tools validates research (Packer et al. 2018); if you use this key to identify organisms for a publication, please cite this work.
Table 1. Checklist of 45 dermestid species reviewed for this key. References to current taxonomic status are cited in the species pages.
|Subfamily: Attageninae Laporte de Castelnau, 1840|
|Tribe: Attagenini Laporte de Castelnau, 1840|
|Attagenus brunneus Faldermann, 1835|
|Attagenus cyphonoides Reitter, 1881|
|Attagenus fasciatus (Thunberg, 1795)|
|Attagenus lobatus Rosenhauer, 1856|
|Attagenus pellio (Linnaeus, 1758)|
|Attagenus rufipennis LeConte, 1859|
|Attagenus unicolor ssp. japonicus Reitter, 1877|
|Attagenus unicolor ssp. unicolor (Brahm, 1791)|
|Novelsis horni (Jayne, 1882)|
|Paranovelsis aequalis (Sharp, 1902)|
|Paranovelsis varicolor (Jayne, 1882)|
|Subfamily: Dermestinae Latreille, 1804|
|Tribe: Dermestini Latreille, 1804|
|Dermestes (Dermestes) ater DeGeer, 1774|
|Dermestes (Dermestinus) carnivorus Fabricius, 1775|
|Dermestes (Dermestinus) fasciatus LeConte, 1854|
|Dermestes (Dermestinus) frischii Kugelann, 1792|
|Dermestes (Dermestes) lardarius Linnaeus, 1758|
|Dermestes (Dermestinus) maculatus DeGeer, 1774|
|Dermestes (Dermestinus) marmoratus Say, 1823|
|Dermestes (Dermestes) nidum Arrow, 1915|
|Dermestes (Dermestes) peruvianus Castelnau, 1840|
|Dermestes (Dermestes) signatus LeConte, 1874|
|Subfamily: Megatominae Leach, 1815|
|Tribe: Anthrenini Gistel, 1848|
|Anthrenus (Anthrenops) coloratus Reitter, 1881|
|Anthrenus (Anthrenus) flavipes LeConte, 1854|
|Anthrenus (Helocerus) fuscus Olivier, 1789|
|Anthrenus (Anthrenus) lepidus LeConte, 1854|
|Anthrenus (Florilinus) museorum (Linnaeus, 1761)|
|Anthrenus (Anthrenus) pimpinellae Fabricius, 1775|
|Anthrenus (Anthrenus) scrophulariae (Linnaeus, 1758)|
|Anthrenus (Nanthrenus) verbasci (Linnaeus, 1767)|
|Tribe: Megatomini Leach, 1815|
|Megatoma (Megatoma) cylindrica (Kirby, 1837)|
|Megatoma (Megatoma) variegata (Horn, 1875)|
|Orphinus fulvipes (Guérin-Méneville, 1838)|
|Reesa vespulae (Milliron, 1939)|
|Trogoderma glabrum (Herbst, 1783)|
|Trogoderma granarium Everts, 1898|
|Trogoderma grassmani Beal, 1954|
|Trogoderma inclusum (LeConte, 1854)|
|Trogoderma serraticorne (Fabricius, 1792)|
|Trogoderma simplex Jayne, 1882|
|Trogoderma sinistrum Fall, 1926|
|Trogoderma sternale Jayne, 1882|
|Trogoderma teukton Beal, 1956|
|Trogoderma variabile Ballion, 1878|
|Subfamily: Thorictinae Agassiz, 1846|
|Tribe: Thaumaphrastini Anderson, 1949|
|Thorictodes heydeni Reitter, 1875|
|Subfamily: Trinodinae Casey, 1900|
|Tribe: Thylodriini Semenov-Tian-Shansky, 1909|
|Thylodrias contractus Motschulsky, 1839|
Table 2. Glossary of selected terms used in the key.
|Declivous: sloping downward|
|Denticle: a small tooth|
|Ensiform: long and narrow with sharp edges and a pointed tip; sword-shaped|
|Fascia: a transverse band or broad line; it is common when it crosses both wings or wing covers|
|Fossa: a deep groove or sinus with sharp edges: specifically applied to grooves on the head or sides of prothorax in which the antennae are concealed|
|Fovea/foveate: a small pit or depression|
|Humerus: the basal exterior angle of elytra|
|Lamina/ae: a chitinous plate or plates|
|Maculation: the ornamentation or pattern of marking|
|Marmorate: veined like a marble, marbled|
|Recumbent: horizontal, laying down|
We thank the reviewers for their helpful comments. We also thank the institutions listed in the methods and the curators who provided the specimens. Reviews by Gary Parsons, Alan Prather, Heather Proctor, and Derek Sikes improved the resulting key.
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