The Cantharidae of Eastern Canada and Northeastern United States
CJAI 25 February 28, 2014
doi:10.3752/cjai.2014.25
urn:lsid:zoobank.org:pub:0D1AF9FE-8898-48CF-B031-4A3783079C69

G. Pelletier & C. Hébert

| Abstract | Introduction | Descriptions of Species | Checklist | Family Cantharidae | Identification Key | Synopsis of Taxa | Acknowledgments | References | PDF | Cite |

Introduction

Cantharidae, also known as soldier beetles or cantharids, are common beetles often found as adults on foliage and flowers, where they feed on insects, nectar and pollen. Several species have been reported to prey on aphid populations infesting plants, shrubs and trees (Way and Banks 1968; Berthiaume et al., 2001; Day et al. 2006), but they can also attack other groups of insects. Indeed, Chauliognathus pulchellus (Macleay) feed on eggs of a chrysomelid beetle, Chrysophtharta bimaculata (Olivier), in Tasmanian forests (Mensah and Madden 1994). Nevertheless, the life history and ecology of most species of Cantharidae are poorly known. For instance, it is known that larvae are mostly carnivorous in the soil (Fender 1973), but their specific prey remain unknown. Using an electrophoretic approach, Traugott (2003) showed that larvae of three Cantharis species fed on earthworms and on dipterous and lepidopterous larvae but much remains to be done to highlight the ecological role of cantharids in terrestrial ecosystems.

Most species emerge in spring or summer and adults are short lived. They are among the most active flying beetles (Ramsdale 2002). They are predominantly active during the day but they may stop activity if temperature becomes too hot (Ramsdale 2002). Many species are also active at night as they were collected in much higher numbers in pitlight traps than in passive pitfall traps (Hébert et al., 2000). Being more exposed to predators on the surface of vegetation, they have developed an effective system of chemical defense (Dettner, 1987). Adults and larvae possess paired tergal glands that secrete repulsive compounds that serve to reduce their palatability to predators (Ramsdale, 2002).

This review was prepared because cantharids were frequently captured in our research projects aimed to determine the impact of forestry practices on beetle diversity in Canadian forests. We hope that the publication of a modern tool for identifying cantharid species will enhance interest on their study and thus increase our knowledge on their life history and ecology. This is strongly needed to help interpreting results in biodiversity projects and to improve our understanding of ecosystem functioning. 
 

Cantharids are easily distinguished from other beetles by their soft elytra and their head which is not completely concealed from above. A total of 473 species belonging to 25 genera have been described so far in North America north of Mexico. McNamara (1991) listed 126 species in Canada and suggested that probably 25 undescribed or unrecorded species remained to be added to our fauna.

The taxonomy of Cantharidae is relatively well known in Canada and the United States due to the extensive work of Kenneth M. Fender, Dorothy McKey-Fender and John W. Green. Cantharis,the nominate genus, was described by Linnaeus in 1758 with C. fusca as the type species. Cantharis rufa and C. livida (both introduced in North America) were among the first species of the family to be named by Linnaeus. Thomas Say described 12 cantharids under the name Cantharis between 1823 and 1835 (Say 1823, 1825, 1835). During much of the 19th century, the name «Cantharidae» was used for beetles now included in the family Meloidae. The first nearctic revision of the family was done by LeConte in 1851 who also described many species of Telephorus, which were then assigned to the subfamily Telephorinae of the larger family Lampyridae, but which are now included in Cantharis and related genera. LeConte described many species of Podabrus between 1850 and 1881 (LeConte 1850, 1866a, 1866b, 1881), as well as some species of Malthinus and Malthodes (sometimes as Malthinus). Fall (1928) revised Podabrus and described many new species. All the primary types of LeConte and Fall are at the Museum of Comparative Zoology, were photographed and are available at http://insects.oeb.harvard.edu/mcz/findrecords.php.

A major revision of Rhagonycha, as a subgenus of Cantharis, was done by Green (1940). Brown (1940) described three new species of arctic Podabrus (now belonging to Dichelotarsus) and Green (1947, 1948) added further contributions concerning that genus. McKey-Fender (1950) partly revised Cantharis (now belonging to Atalantycha and Rhaxonycha). However, since those publications, the former genus Cantharis has been divided into five different genera: Atalantycha (Kazantsev 2005), Cantharis, Pacificanthia (Kazantsev 2001), Rhagonycha (Fender 1971) and Rhaxonycha (Ramsdale 2002). More recently, Dichelotarsus, described by Motschulsky in 1860, and long considered as a subgenus of Podabrus in Europe, was restored by Kasantsev (1992). Fender (1951) produced a major contribution concerning Malthodes that included all eastern North American species. Trypherus, then newly discovered in Canada,was revised by Fender (1960). Finally, Green (1966) revised Silis (including the species now in Ditemnus), described many new species, but none in our area. Downie and Arnett (1996) provided keys and brief descriptions of northeastern North American species.

Cantharids are widely distributed in North America north of Mexico. Atalantycha, which contains three species, is found only in eastern North America. Rhagonycha, Podabrus, Dichelotarsus and Cantharis are widely distributed, with the former two genera being more diversified in the east and Dichelotarsus more highly diversified west of the Rocky Mountains. Silis and Ditemnus are more diversified in southwestern North America. The large genus Malthodes is mostly diversified in western and southern North America, with relatively few species in the northeast. Members of Chauliognathus are mainly found in the south with only two species in Canada. 

Cantharidae is found in a wide variety of habitats. Over the last 20 years, we sampled hundreds of forest stands throughout the province of Quebec. Based on these studies and on specimen labels from various collections, we can categorize Podabrus and Dichelotarsus as general forest dwellers. Atalantycha and Silis were mostly found in hardwood forests and Pacificanthia in conifer forests. Rhagonycha is more diversified in hardwood and pine forests, marshes and shrubby areas. Cantharis and Chauliognathus are common in grasslands and forb fields. Malthodes is common in mixed and conifer forests in eastern North America.

Cantharid seasonality can also be overviewed on the basis of specimen labels.  Atalantycha can be found early in spring from April to May in Canada. Most cantharids (Podabrus, Dichelotarsus, Rhagonycha, Malthodes) are very active in June, with populations decreasing in July. However, Silis, Ditemnus and Polemius are predominant in July and Chauliognathus pensylvanicus is mostly seen in August and September.

This publication covers 114 described species that are found in eastern Canada and northeastern United States, as defined by Downie and Arnett (1995). The region covered includes Newfoundland west to Ontario, south to New Jersey, Pennsylvania, Ohio, Indiana, Illinois and Wisconsin. All known species found in Manitoba and Minnesota are also included as they bordered Ontario.

All the types of LeConte and Fall were verified by the senior author. However, four species described by Miskimen (1956) from Ohio, three belonging to Rhagonycha and one to Dichelotarsus,have not been verified with the types and have not been incorporated into the key. Two of these species were described from a single specimen and in one case from the female only. Kazantsev’s (2004) list of Cantharidae of the former USSR was checked in order to verify if some of our Arctic species could be synonymised with some Palearctic species. Four species were suspected as potential synonyms and specimens of two Palearctic species were borrowed from European museums to compare with our Nearctic species (the two other species could not be found).

This publication is available in PDF format as well as an interactive identification key online. This digital key will lead to images that can be selected in order to progress to the final diagnosis of the species. For each species, a brief description is provided as well as images of the habitus and genitalia (for Malthini and few other groups) and often field photographs. Species variations, comparison with similar species, habitat, ecological data, seasonality, and distribution maps are also given. Photographs of habitus or morphological structures were taken with a Nikon Digit-like Camera DMX 1200F through a Nikon SMZ 1500 stereoscopic microscope. All photos were processed through a Proscan II system by Prior, which combines all images taken at different layers into one focused image. Each body part (head, thorax, elytra, antennae, legs) of each species was photographed individually and then joined together using Adobe Photoshop software.

Though species are well defined taxonomically, existing keys for many genera can be used only for identifying males. Some characters used in the previously published keys were complex and confusing, making identification of many species difficult. As an example, Green (1940) only used claws of the first pair of legs of males in Rhagonycha (as Cantharis) to separate many species because of the great variability of this character. However, for many species, according to our data, males usually represent about 20% of the adult population and not more than 1% in Rhagonycha fraxini. In such cases, the available identification keys are almost useless for separating most specimens. For that reason, we decided to use the claws of the metathoracic legs of both sexes, which are similar and less variable but, combined with other characters, like the front margin of the clypeus, elytral pilosity and pronotum shape, help to separate all species in both sexes. We hope that this publication will help students, amateurs, technicians and entomologists to easily identify most species, including female specimens.

Most cantharid specimens in the Canadian National Collection, in Ottawa, were examined. Many specimens from Quebec came from the biodiversity project led by Christian Hébert at the Laurentian Forestry Centre. Steve Marshall from the University of Guelph provided many specimens and some ecological data from Ontario. Reggie Webster also provided specimens from New Brunswick to complete the picture. Claude Chantal and Michel Racine gave a substantial number of specimens from Quebec for identification or confirmation.

Live pictures were used with permission of authors from the Bug Guide site (http://bugguide.net/node/view/118/bgpage). Steve Marshall also provided a substantial amount of images for this publication.