Canadian Journal of Arthropod Identification

The Cantharidae of Eastern Canada and Northeastern United States
CJAI 25 February 28, 2014

G. Pelletier & C. Hébert

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



Descriptions of Species

Both sexes are described together and not separately as in Green (1940). When there is sexual dimorphism, females are described first because they are usually more numerous than males in the majority of species. Length is measured from the anterior margin of the clypeus to the apex of the elytra. When measuring, you need to consider that the apex of the elytra is often folded downward and this folded area must be extrapolated in the calculation. All characters necessary to identify the species (diagnosis) are bolded in the text.

Each part of the beetle is described in this sequence: head (including eyes, clypeus, mandibles, palpi, antennae), thorax (pronotum, sternum, legs) and abdomen (elytra, ventrites), describing coloration first, then morphometry and other structural characters. Eyes/head width ratio is calculated by dividing the distance between eyes (frons width) at the level of maximum head width by the head width (from dorsal view) and subtracting the result from 1: 1-(FW/HW) where FW=frons width and HW=head width. This ratio of eyes/head width is calculated for both females and males because males have larger eyes than females. The clypeus can be notched, biarcuate, sinuate or rectilinear. Antennae/body length ratio is calculated for many genera. The third and second antennomeres length ratio (A3/A2), both for females and males, is also recorded.

Pronotum color, width/length ratio, margin and tubercle shapes, surface porosity, punctures and pubescence are noted. Width/length ratios of pronotum go from subquadrate (1:1) to 2X as wide as long. Lateral margins can be arcuate, sinuate, rectilinear, subparallel, incised or irregularly modified (in males of Silis and Ditemnus). Anterior angles can be arcuate or angulate. Many species have two distinct tubercles near basal margin, often prominent and with distinct characteristic shape (Podabrus, Dichelotarsus). Pronotum can be glossy, subglossy or opaque (with distinct microsculpture) with strong, moderate or sparse punctures. Pubescence is usually moderately long and sparse but sometimes very short and dense. Coloration of prosternum, meso-, metaventrite and scutellum are mentioned. Leg coloration is described followed by the character state of the tarsal claws of both females and males which can be simple, cleft or toothed at base.

Elytra coloration, length/width ratio and the elytra/pronotum length ratio are given. In many cases, the elytra are folded on the sides (costal margins) and at the apex, which make morphometric measurement difficult and modify its shape. As an example, Rhagonycha fraxini has elytra with their lateral margins divergent, but because the elytra are folded on the sides, the lateral margins will look subparallel. Some other species have the elytra separately arcuate at the apices but because they are folded apically, they appear truncate. The elytra need to be examined laterally and posteriorly to verify if the foldings give a biased appearance to the shape. The elytra can have the lateral margins subparallel, divergent, or rarely convergent. The surface can be scabrous or rugose with the pubescence dense, moderate or sparse, erect or/and prostrate. In some cases, mostly in Malthini, median lobe of aedeagus and subgenital plate of the male are described. In Malthini, males have the aedeagus exerted in dried and mounted specimens. In Cantharini and Podabrini, median lobe of aedeagus of most species are illustrated but not described.

Finally, colour variations are noted in many species, which can easily lead us to confuse several species. Variations in body shape are essentially due to specimen preparation artifacts because of their soft body. All similar species related to the one described are mentioned with characters that can help to separate them, starting with the most similar species. These characters are usually mentioned in the key.

Distributions are given from eastern Canada and northeastern USA to the northwest down to the southeast and then to the southwest, including the range outside the geographic scope of this work. Distribution maps are given for each species and are overlaid on Canadian ecozones and US ecoregion maps, as defined below. However, for simplication, some ecozones/ecoregions were grouped. All names come from ArcGIS map software from ESRI. In Canada, the ecological framework comes from Agriculture and Agri-Food Canada and Environment Canada ( In the United-States, it is a modification of Bailey’s ecoregions from USDA Forest Service ( Legend for ecozones/ecoregions outside the scope of this work is not described below.

Arctic zone, in northern Canada (including most Arctic Ocean islands) to Alaska, from coast to coast, covered mostly by toundra.
Taïga zone, also called Subarctic and sometime Hudsonian zone, bordering south of the Arctic zone, from coast to coast, covered mostly by open Black Spruce forest growing sparsely on lichen.
Boreal zone, also called Canadian zone, mostly covered by dense Black Spruce forest, more dominated by Balsam Fir in the south, extending nearly coast to coast.
Mixedwood Plain zone, mostly covered by deciduous forests predominating by maple-beech, but also mixed forests with White Pine and Red Oak in wet areas, along the St-Lawrence River and the Maritime provinces and states. This area is mostly covered by agricultural lands.
Northern Appalachian zone, including Atlantic Maritime zone of Canada, mountain chain extending from eastern Quebec, New Brunswick south to western Massachusett, Connecticut and Adirondack Mountains of New York, a southern extension of the Boreal zone, dominated by spruce-fir and maple-beech forests.
Southern Appalachian zone, (also called Alleghanian zone), mountain chains extending from Pennsylvania to north Georgia and Alabama, including Ozark mountain of Missouri and Arkansas, southern extension of the northern Appalachian and the Mixedwood zones, covered by maple-beech forests but with higher proportion of pine and oak-hickory forests. Spruce-fir forests can be found in highest mountains.
Southeastern USA Forest Plain zone (also called Carolinian zone), extending south of the Mixedwood and the Southern Appalachian zones, from New Jersey to north Florida west to Illinois, Arkansas and Texas, predominating by pine and oak-hickory forests.
Southeastern USA Coastal Plain zone, (including the Mississipi Alluvial and Southeastern USA Coastal Plain, the Texas-Louisiana Coastal Plain, bordering the Atlantic and the Gulf of Mexico seashore south of the Southeastern Forest Plain zone, from New Jersey to Florida west to the Mississipi valley and Texas, predominating by vast pine forests and evergreen hardwood forests predominated by oak.
Prairie zone, excluding South Central Semi-Arid Prairie, west of the Boreal, Mixedwood Plain and Southeastern USA Forest Plain zones, from southern Manitoba to Alberta south to Missouri, Kansas, Nebraska, and Wyoming, predominated by grasslands and meadows.
Montane Cordillera, including the cordillera of western USA, from British Columbia and western Alberta south to Colorado, New Mexico, Utah, Idaho and California, predominated by ponderosa and lodgepole pines, very diversified area containing many endemic species, but also extending range of few eastern species.

Habitats, when known, are reported for each species. However, as ecological data were not recorded systematically by collectors in the past, habitats remain unknown for about 20% of the species in the area covered. However, after the 1992 Earth Summit in Rio de Janeiro, Brazil, a structured biodiversity research program was launched at Laurentian Forestry Centre of the Canadian Forest Service and habitats of many species, mostly in eastern Canada, began to be better known. Our program allowed increasing knowledge for species living in spruce, fir and maple forests. Moreover, specimen label data were useful for improving knowledge of other species living in grasslands, open shrubby fields and orchards which are relatively well known. However, though some species have been recorded in these habitats, oak and pine forests still need to be more intensively investigated, as well as freshwater and coastal marshes and bogs.

Seasonality is based on data from labeled specimens collected mostly in eastern Canada. For species with high number of specimens, the information is much more detailed, including specification about peak of activity. Finally, the number of specimens examined is given to indicate the relative abundance of the species in collections as well as the proportion of females and males to indicate the relative scarcity of males in some species. Females usually outnumber males in collections.