|Syrphus attenuatus |
Mostly boreal regions, but some records from mixed forest (Vockeroth 1992).
Adults collected during spring/summer months (May-September).
Approximately 7 to 15 mm in length, black and yellow abdomen with a yellow face. Lateral margins of abdominal tergites narrowly, subtly but continuously yellow (see A on image; this can be very faint, especially on older specimens). Males: The upper half of frons dark gray and covered with a waxy, whitish powder (i.e. pruinose), with lower half of frons dark to light yellow. Hind femur is either entirely yellow, or the basal half is black and the rest is yellow. The wing membrane is entirely covered with tiny hairs (i.e. trichose). One or both of tergites 3 and 4 with either widely or narrowly separated yellow spots (see B on image). Females: Similar to male, but all femora entirely yellow, face yellow, frons similar to male but only lower one-third of frons bright yellow (Vockeroth 1992).
Poorly known, but probably multivoltine, although northern populations may be univoltine (Vockeroth 1992). The overwintering stage is unknown, but is probably the last larval instar, as is the case with several related species (Schneider 1969). Host choice of the aphidophagous larvae is probably mostly determined by the oviposition behaviour of the females, because the dispersal capabilities of most Syrphus larvae are relatively limited (Sadeghi and Gilbert 2000a,b). Females of a related species (S. corollae) were found to oviposit in response to the sole presence of aphid honeydew (Schneider 1969), although females may use both visual as well as olfactory signals for choosing an oviposition site. Females in this genus tend to choose large or growing colonies of aphids, to ensure a plentiful food source for their offspring (Sadeghi and Gilbert 2000a). Larvae are probably voracious predators, and parasitiods are unknown, although many parasitoids of other members of the genus Syrphus have been recorded, including (amongst many families) members of the Braconidae, Chalcididae, Proctotrupidae, Encyrtidae, and Ichneumonidae (particularly the subfamily Diplazontinae) (Schneider 1969).
Not of concern.
Poorly known, but like all members of the genus Syrphus, larvae are aphidophagous and probably polyphagous, choosing aphid hosts on many species of shrub, herb, and tree (Vockeroth 1992). This is suggested by their broad distribution through several different habitats. Adults probably feed on pollen and nectar of flowers.
Widespread throughout Canada, from southern B.C. north to Nunavut, across central Canada well as in Quebec. U.S. records include Alaska, Colorado, Wisconsin, and Pennsylvania. Also found in Northern Europe (Vockeroth 1992).
In Canada, 27 male specimens and 52 female specimens have been identified (Vockeroth 1992).
|species page author||Wins-Purdy, A.||2005 |