Great Black Wasp

Appearance

''Sphex pensylvanicus'' is a large, black wasp, significantly larger than their congener ''Sphex ichneumoneus'' . Males are smaller than females, at only 19–28 mm long compared with typical female sizes of 25–34 mm.

According to John Bartram, "The sting of this Wasp is painful, but does not swell like others". As well as being larger than ''S. ichneumoneus'', they are also darker, with smoky wings and an entirely black body, where ''S. ichneumoneus'' has yellow wings, red legs, and a partly red abdomen.

Distribution

''S. pensylvanicus'' is distributed across most of the contiguous United States and northern Mexico. During the late 20th century, its range expanded north to New York and the Canadian provinces of Quebec, Ontario, and Nova Scotia.

Behavior

''S. pensylvanicus'' is an important pollinator of plants including the milkweeds ''Asclepias syriaca'' and ''A. incarnata''. It has also been reported on ''Daucus carota'', ''Eryngium yuccifolium,'' ''Melilotus albus,''''Monarda punctata'', and ''Pycnanthemum virginianum'' ''S. pensylvanicus'' is one of several species of ''Sphex'' to be parasitized by the strepsipteran ''Paraxenos westwoodi''.

Reproduction

Adult females of ''S. pensylvanicus'' build an underground nest which they provision with various orthopteran insects, particularly of the genera ''Microcentrum'', ''Amblycorypha'' and ''Scudderia''. Prey are stung three times, once in the neck and twice in the thorax, and are paralyzed by the wasp's sting, although they can survive for weeks.

The prey are then carried to the nest. While collecting their prey, the females are vulnerable to kleptoparasitism, in which birds, including the house sparrow and the grey catbird, steal the prey that the wasp has collected.

The eggs of ''S. pensylvanicus'' are 5–6 mm long and 1 mm wide; they are glued to the underside of the prey insect between the first and second pairs of legs. Each of the several chambers in the nest houses a single larva, which consumes 2–6 katydids or grasshoppers. The larval stage lasts 10 days, reaching a pre-pupation size of 30–35 mm long by 7–10 mm wide.

Evolution

''Sphex pensylvanicus'' was the subject of the first article on an insect written by a native of the New World, when observations made by John Bartram on ''S. pensylvanicus'' were presented to the Royal Society in 1749 by Peter Collinson. ''Sphex pensylvanicus'' was described by Carl Linnaeus in his 1763 work ''Centuria Insectorum'', using material sent to him by Charles De Geer.