Canadian Journal of Arthropod Identification

The Cryptophagidae of Canada and the northern United States of America

CJAI 40 -- December 20, 2019

Georges Pelletier & Christian Hébert

An Editorial Corrigendum has been published for this paper doi:10.3752/cjai.2019.40ed.

| Abstract | Introduction | Materials & Methods | Checklist | DNA Barcoding | Taxonomy | Key to Species | Acknowledgments | References | PDF | Cite |
| Supplemental Material |

Materials & Methods

This publication covers all 142 described species that can be found in Canada and the northern United States of America. Types of most species described by Casey (1900) (except for species of Cryptophagus)were examined and photographed by GP, and are redescribed according to the current standards. A list of types and other material examined (with their original name) from various institutions, including synonymies (names in bold are still valid today) and new combinations is provided in the supplemental materials. Types of most species described by Casey (1900) (except for species of Cryptophagus) were examined and photographed by GP, and are redescribed according to the current standards. Unfortunately, it was not possible to examine holotypes of Palearctic species held in European collections. Our concept of Holarctic species follows Woodroffe & Coombs (1961) for Cryptophagus and Johnson (1992) for Atomaria and some species of Cryptophagus that were renamed since Woodroffe & Coombs (1961).

Also, collaborations were made with Richard Leschen and Colin Johnson, two world specialists of the family working on a world checklist. They compiled the Palearctic checklist, including all known species from Europe, Asia and North Africa, (Johnson et al. 2007 – including an unpublished 2014 update). This list gives a broad view of the family, including all species that could potentially be found in North America. From that list, we selected all species with an extensive distribution that could potentially be introduced into North America, and all northern species that could potentially be present in northern Canada and Alaska (Supplemental Materials).

The present publication is available in PDF format along with an online interactive identification key. For each species, a detailed description and image of the habitus, sometimes an image taken in the field, habitat data, some ecological data and a distribution map are provided. Photographs of habitus or morphological structures were taken using a Nikon digital camera DMX1200F through a binocular Nikon SMZ. All photos were processed through a Proscan II system by Prior Scientific (, which stacks all images taken at different layers into one focused image. Each part (head, thorax, elytra, antennae, legs) of all species was photographed individually, in order to improve the resolution, and then joined together using Adobe Photoshop Element software. Images of the following Palearctic species, either introduced or Holarctic, were provided by Lech Borowiec from the University of Wroclaw (see Supplemental Materials for additional related material examined):

  • Caenoscelis subdeplanata Brisout de Barneville
  • Cryptophagus dentatus (Herbst)
  • Cryptophagus laticollis Lucas
  • Cryptophagus lycoperdi (Scopoli)
  • Cryptophagus scutellatus Newman
  • Henoticus serratus Gyllenhal
  • Telmatophilus typhae Fallén
  • Atomaria (Anchicera) apicalis Erichson
  • Atomaria (Anchicera) fuscata (Schönherr)
  • Atomaria (Anchicera) lewisi Reitter
  • Atomaria (Anchicera) mesomela (Herbst)
  • Atomaria (Anchicera) pusilla (Paykull)
  • Atomaria (Anchicera) testacea Stephens
  • Atomaria (Atomaria) elongatula Erichson
  • Atomaria (Atomaria) fimetarii (Fabricius)
  • Atomaria (Atomaria) linearis Stephens
  • Ephistemus globulus (Paykull)

Most specimens from the Canadian National Collection in Ottawa were examined. Many specimens from Quebec came from biodiversity projects led by Christian Hébert at the Laurentian Forestry Centre. Claude Chantal, who holds the largest private beetle collection in Quebec, provided a substantial number of specimens from Quebec for study. The Northern Forestry Centre in Alberta (Dave Langor, James Hammond), the University of British Columbia (Karen Needham), the University of Georgia (Richard Hoebeke) and University of Alaska (Derek Sikes) also provided us with numerous specimens. Steve Marshall from the University of Guelph provided a few specimens and some ecological data from Ontario. Reggie Webster also provided a few specimens from New Brunswick.

The genera of Cryptophagidae are well defined taxonomically, thanks to Leschen (1996). Johnson (1992) has developed a useful key to identify most species from central Europe; however, no existing key can help identify all species found in Canada, especially those of the genus Atomaria. We simplified the key of Woodroffe and Coombs (1961) on Cryptophagus,and it should help easily identify nearly all specimens found in Canada and the USA. We hope that this publication will help students, amateurs, technicians and professional entomologists to easily identify most species.

This review was prepared because of the increased interest and research activities (mainly biodiversity projects) related to cryptophagids. We believe that many species can be good ecological indicators for old growth forests as these forests may be subject to more extensive decaying processes involving fungi, the main food source of cryptophagids. Do these beetles, by their activities, limit the growth of mycelium and protect the trees by limiting the spread of tree diseases or, on the contrary, disperse the spores of the fungi and accelerate the decaying process of the forest? The answers to those questions are unknown for the moment but increasing the knowledge of this family and knowing which species can be found in which types of forest, at which stage of maturity or decay, will help to provide some answers in the future.

Interactive keys for species determination

The interactive key was created to facilitate the determination of all species of Cryptophagidae in Canada, Alaska and northern mainland USA (south to Maryland west to Oregon), covering all habitats that can be found in Canada. This key includes all known Nearctic Atomaria. However, a few doubtful species of Atomaria introduced from Europe and previously recorded in North America, but not seen in our material, are not included in this work.This includes the following species:
  • Atomaria (Atomaria) diluta Erichson
  • Atomaria (Atomaria) nigriventris Stephens

Atomaria lepidula was described by Mäklin from Alaska; however, the holotype, stored in the Finnish Museum of Natural History, examined and returned by Colin Johnson in 1971, has been lost. According to its original (very short) description in Latin, this species belongs to the subgenus Anchicera, is a uniform reddish brown and is very large in size for the genus (2.4 mm). No specimen with these characters was seen in our material so this name will be considered a nomem dubium.

The interactive key uses external morphological characters that are very useful to identify all species. The most useful diagnostic characters include antennae, mainly the first segment’s (A1) shape and length relative to the second, club A9-A10 shape (subquadrate, slightly to strongly transverse), sometimes the shape of A4-A8, pronotum shape and proportions, elytra shape, proportions and pilosity, and sometimes colour pattern.

Genitalia, which are useful to confirm the identification of species in many beetle families, are not very useful for Cryptophagidae; however, DNA barcoding has been by far a better method to separate species without the risk of destroying specimens (needing only to remove one leg). The DNA barcoding method will be explained in a later section.

Descriptive plates of species

In order to facilitate the identification of the species, all diagnostic characters are in bold, including all major sections of the description: length (L), head, antennae, pronotum, elytra. After the description, each species is compared with the most closely related one or any other species which can be confused.
Both sexes are described together. Species of Cryptophaginae only have slight sexual dimorphism in the tarsal formula, being 5-5-4 in male and 5-5-5 in female. In a few species, such as Caenoscelis antennata, sexescan be also separated by their antennal structure. However, only the presence of tenant setae in claws of males can separate the sexes of Atomariinae for all species. Total length of the species is measured from the tip of the clypeus to the tip of the elytra or abdomen.

Each part of the beetle is described in the following sequence: head (including eyes, mandibles, palpi, clypeus, antennae), thorax (pronotum, sterna, legs, elytra), and abdomen (sternites), describing colouration first, then morphometry and other structural characters. Eyes/head width ratio is calculated by dividing the distance between the internal eye orbits at the level of maximum head width (FW: frons width) by head width from dorsal view (HW) and subtracting the result from 1: 1-(FW/HW). The clypeus is quadrate, without any significant difference between genera or species. Antennae (A) are described in detail, including the shape and relative length of each article compared to the following one (A1-A8) and the relative width of club articles (A9-A11). Antennal description is important to separate species groups and sometimes species.

Pronotum colour, width/length ratio, margin shapes, surface porosity, punctures and pubescence are noted. Width/length ratios of pronotum are measured from maximum width and length at the middle. This ratio can vary from subquadrate (1:1) to twice as wide as long (2:1), with only one species being elongate (Hypocoprus latridioides). Lateral margins can be arcuate, sinuate, straight, subparallel, dentate, crenulate or with a callosity at anterior angles. Pronotum shape and width/length proportion are crucial for the diagnosis of most species. Pronotum is usually glossy, subglossy or rarely opaque (with distinct microsculpture) with strong, moderate or sparse punctures. Pilosity is usually moderately long and sparse but sometimes more dense. Colouration of the sterna (including prosternum, meso- and metaventrite), scutellum and legs is mentioned.

Elytra colour, length/width ratio and elytra/pronotum length ratio are recorded. Elytra often have sides entirely arcuate or straight and divergent at the anterior half or more, rarely subparallel but usually arcuate and convergent at apical half or less. Surface is usually glossy and pilosity is dense, moderate or sparse, long or short, erect, suberect, appressed or prostrate, sometimes both. Abdominal sternite colour is noted. All males have internal genitalia and there is no external dimorphism feature on the abdominal ventrites.

Colour is not very useful to separate most species. Many species have a uniform reddish brown body. Many others have a dark brown head and pronotum combined with yellowish brown elytra. A few species are entirely dark brown to black or entirely yellowish brown. A few species have a constrasting black pattern on paler elytra. Some species such as Atomaria fuscata Schönherr can be very variable in colour, being entirely reddish brown to dark brown. All colour variations are mentioned in the text for each part of the body when necessary. Antennal structure, pronotum and elytra shape have been used to separate most species. Color is mostly used as a confirmation character when there is not much variation within a species except in distinctly patterned species. 

Similar species related to the one described are mentioned with all the characters that can help to differenciate between them, starting with the most similar species. All the characters discussed above are usually mentioned in the key.

Distributions are given from eastern Canada to the northwest, including Alaska, down to the southeast and the southwest, including the range outside the geographic scope of this work, both for species occurring in Canada and for species that have not yet been recorded in Canada but that occur in the USA. All distribution maps indicate ecozones (Figure 1), as defined below; however, for the sake of simplicity, some ecozones were grouped together in order to correspond to most species’ distributions.

Arctic zone, northern Canada from coast to coast (including most Arctic Ocean islands) and Alaska, covered mostly by tundra.

Taïga zone, also called Subarctic and sometimes Hudsonian zone, bordering south of the Arctic zone, from coast to coast, covered mostly by open black spruce forests growing sparsely on lichen.

Boreal zone, also called Canadian zone, mostly covered by dense black spruce forests, mostly dominated by balsam fir in the south, extending nearly coast to coast.

Mixed Wood Plains zone, also called Transition zone, mostly covered by deciduous forests dominated by maple and beech, but also by mixed forests with white pine and red oak in more humid areas along the St. Lawrence River and in the Maritime Provinces and states. This area is mostly covered by agricultural lands and many prairie species expand their distribution eastward in that region.

Northern Appalachians zone, includes the Atlantic Maritime zone of Canada, a mountain chain extending from eastern Quebec and southern New Brunswick to western Massachusett, Connecticut, and the Adirondack Mountains of New York; a southern extention of the Boreal zone, dominated by spruce-fir and maple-beech forests.

Southern Appalachians zone, also called Alleghanian zone, a mountain chain extending from Pennsylvania to north Georgia and Alabama, including the Ozark Mountains of Missouri and Arkansas; a southern extention of the Northern Appalachian and Transition zones, covered by maple-beech forests, but with a higher proportion of pine and oak-hickory forests. Spruce-fir forests can be found on the highest mountains.

Southeastern USA Forest Plain zone, also called Carolinian zone, extending south of the Transition and the Alleghanian zones, from New Jersey down to northern Florida and west to Illinois, Arkansas and Texas, dominated by pine and oak-hickory forests.

Southeastern USA Coastal Plain zone, also called Louisianian zone, including the Texas-Louisiana Coastal Plain, bordering the Atlantic Ocean and the Gulf of Mexico seashore south of the Carolinian zone, from New Jersey down to Florida west to the Mississipi Valley and Texas, dominated by vast pine forests and by evergreen hardwood forests dominated by oak.

Temperate Prairie zone, excluding the South Central Semi-Arid Prairie zone, west of the Boreal, Mixed Wood Forest and Southeastern USA Forest Plain zones, from southern Manitoba west to Alberta and south to Missouri, Kansas, Nebraska, and Wyoming, dominated by grasslands and meadows.

Western Cordillera zone, including the cordillera of the western US, from western Alberta to British Columbia, south to Colorado, New Mexico, Utah, Idaho and California; dominated by Ponderosa and lodgepole pines, it is a very diversified area that contains many endemic species, and also extended range of a many northern species.

Marine West Coast Forest zone, a narrow strip along the Pacific Coast from southern Alaska and British Columbia south to northern California; dominated by large conifers such as Douglas-fir, Sitka spruce, western cedar and western white pine.

Other ecozones are recorded, but are only represented by a smaller number of species or have not been adequately sampled.

The distribution pattern of a species does not follow political borders. Our ecozone map system has been especially designed to give a more relevant idea of the likely distribution of a species. When a species is present only in the eastern and the western part of an ecozone, especially in a relatively undisturbed ecozone like the Boreal zone, the probability is very high that it will be eventually collected in between. The main reason why many species have not been reported from northern Ontario, Manitoba and Saskatchewan is because these areas have not been as intensively sampled as in Quebec or Alberta. However, if two specimens have been collected in two distant localities belonging to two different ecozones, the probability that one of these is an accidental introduction is much higher. In that case, we cannot argue for a real continuous distribution.

We include an index of commonness of a species. This mainly reflects the number of specimens seen in collection, which does not necessarily translate to reality in the field, especially for species living in very remote areas or in specialized habitats:

  • Very common: more than 300 specimens seen;
  • Common: between 100 and 300 specimens;
  • Fairly common: between 50 and 100 specimens;
  • Uncommon: between 10 and 50 specimens;
  • Rare: fewer than 10 specimens.
Table 1 represents a list of all species of Cryptophagidae found in Canada and the northern USA together with their respective ecozones. The results of this table show that the most well diversified ecozones for Cryptophagidae are the Boreal (100 species), Western Cordillera (97 species), Mixedwood Plain (81 species) and Northern Appalachian (76 species). Of course, these ecozones were intensively sampled by three different Canadian Forestry Service centers.

Seasonality is also recorded, mentioning at first the wider time distribution pattern based on extremes of collecting dates, followed by the usual period of adult activity including their peak for common species, all shown in a bar graph. However, for species represented by less than 20 specimens, no bar graph is shown.

Habitats and host trees or plants, when known, are also noted for each species. Most collectors before 1980 did not record any ecological data for most specimens. Since 1992, when biodiversity started being considered in CFS research studies, habitats of many species have begun to be known. Most species living in spruce, mixed fir-birch, and maple forests are now well known. Other species living in grasslands, open shrubby fields and orchards are also relatively well known. However, although some species have been recorded in these habitats, oak and pine forests still need to be more deeply investigated, including freshwater and coastal marshes and bogs. Today, habitats are known for about 85% of the species. Finally, the geographic distribution of the species and the presence of better-known species in the same locality collected on the same date can help us to determine the probable habitats of a determined species, though that information will need to be verified by further research. Except otherwise noted, most habitat data were recorded from specimen labels. Finally, the number of specimens examined is given to indicate the relative abundance of the species in the collections.

Figure 1. Nearctic ecozones.