University of Alberta E.H. Strickland Entomological Museum
SeasonalityAdult specimens in the Strickland Museum were collected in May and June.IdentificationBoth male and female adults of P. borealis are 11-19mm long (Green 1957). Their elytra are dark brown with very narrow to obliterated pale margins and a pale elytral suture. The pronotum is subpentagonal in shape, lighter than the elytra, with a dark median vitta (stripe) and sometimes with rosy patches. The lateral edges of the pronotum also have dark vittae, which are often pale and difficult to notice in some specimens. Pyractomena borealis can be differentiated from all other Alberta fireflies, except P. dispersa, by the presence of light organs, which appear as two pale, enamel-like ventral abdominal segments in the male. The female has enamel-like organs confined to the edges of these same segments. The extent of secondary elytral pubescence is useful in differentiating P. borealis from other Pyractomena species. In Pyractomena borealis, this secondary elytral pubescence (very tiny hairs, which give the elytra a dusty appearance) is present on most of the dorsal elytral surface, extending from the apex to about the basal quarter. In some specimens, this pubescence extends further, with only the basal 1/6th of each elytron appearing glabrous. Pyractomena borealis larvae are campodeiform, 17-22mm long in the 5th (last) instar, quite hard bodied, and somewhat flattened dorsoventrally. First instar larvae measure 3.5-4.5mm (Archangelsky 1998). Larval colour ranges from dark brown to brick red, and the pattern can be variegated (Arnett 2001). The abdomen narrows gradually to the 10th (last) segment, which is very small and contains the larval hold-fast organ. This structure is like a posterior foot; it has 10 protractible finger-like structures, each covered in tiny hooks, which allow the larvae to grasp surfaces or objects. The head of these larvae is long and narrow, and can be fully retracted into the thorax (Archangelsky 1998).
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Taxonomic Hierarchy for University of Alberta E.H. Strickland Entomological Museum