|Syrphus ribesii |
Variable; mixed forests, gardens, meadows, and fields (Laska and Stary 1980).
Adult flight ranges between April and October in Canada.
Approximately 7 to 16 mm in length, black and yellow body. Eye bare, face yellow. Distinguishing between S. ribesii and S. vitripennis is quite difficult, however S. ribesii has the bm cell entirely covered with tiny hairs (i.e. trichose, see A on image) (Gilbert 1986). All specimens have tergites 3 and 4 with a yellow band rather than spots; these bands are usually complete but slightly divided in the middle in some specimens (see B on image), with this species generally showing a lot of variation in the shape of abdominal bands (Vockeroth 1992). Males: Frons usually completely dark, although it may be yellow on bottom one-fifth on some specimens. Hind femur either yellow or black on basal two-thirds. Females: Similar to males, although mid and hind femora only black right at base, with most specimens having a hind femur that is completely yellow (Vockeroth 1992).
Syrphus ribesii is oligovoltine in England, with either two or three generations per year, and overwinters as a cold-tolerant larva (Sadeghi and Gilbert 2000a). However, it has also been reported to migrate in large numbers to the Mediterranean to overwinter (Gilbert 1986). It is a common and voracious predator, and can have a significant effect on the natural regulation of aphid populations. Males can be heard to make an audible noise with their wings as they vibrate them rapidly to warm up their thoracic muscles for flight; this is presumably to maximize the chances of catching a female, as mating occurs mid-flight and lasts as little as two seconds (Gilbert 1986). After pupation, emerged adult females are able to oviposit 7 to 8 days post-eclosion (Sadeghi and Gilbert 2000b). Much work has been done on the oviposition preference of the females of this species, with females showing a strong preference to oviposit near sycamore aphids, rose aphids, and pea aphids when given a choice of eight species (Sadeghi and Gilbert 2000b). Many parasitoids of S. ribesii are also known, including (amongst many families) members of the Braconidae, Chalcididae, Proctotrupidae, Encyrtidae, and Ichneumonidae. In particular, the Ichnuemonid Diplazon laetatorius is a common enemy, and S. ribesii larvae have evolved many defences against them. The remain still when they detect parasitiod antennal tapping, and emit a sticky oral substance if an ovipositor is inserted. Finally, they will assume a crescent shape and roll over if an attack persists (Rotheray 1981).
Widespread and common, not of concern.
Larvae are aphidophagous and polyphagous, and feed on a wide range of aphid species. In North America, larvae have been recorded on several species of Aphis and Microsiphum, as well as on Pemphigus populicaulis, Cinara hottesi, C. carolina, and C. lasiocarpa (Vockeroth 1992).
Widespread throughout Canada, and from Alaska down to Mexico and Central America. It is also found in much of Europe, as well as Asia (Vockeroth 1992).
For a clear description of an effective and simple method for rearing S. ribesii see Frazer (1972).
|species page author||Wins-Purdy, A.||2005 |