Above left: a species of Ectemnius a genus of solitary wasp, from which Jennifer Owen found 5 species in her garden.
Above right: nests of a crabronid wasp, Passaloecus eremita, in woodworm tunnels, some completed and sealed with pine resin.
The adults of some solitary wasp species will visit flowers to feed on nectar and pollen. Some female solitary wasps are capable of stinging people if roughly handled, but use of the sting is normally confined to subduing the insects and spiders collected to stock the wasps’ nests.
Spider wasps lay a single egg on each stored spider, on which the wasp larva will subsequently feed. Other solitary wasps also have larvae that feed on the food insects or spiders provided by the mother wasp. When fully fed, solitary wasp larvae spin silk cocoons and pupate within the nest. There is usually one generation a year, overwintering as pupae and emerging as adult wasps in the following summer.
Role of solitary wasps in gardens
Some of the insects collected to provision nests, such as aphids, leafhoppers and caterpillars are potential pests of garden plants. A crabronid wasp, Cerceris arenaria, stocks its nests with adult vine weevils, which is a great help to gardeners. However, some solitary wasps collect hoverfly species that have larvae that prey on aphids, so the overall benefit in terms of reducing pest insects may be limited.
Other sources of information
Yeo, P and Corbet S. (2015) Solitary Wasps. Naturalists Handbooks 3 Pelagic Publishing
Archer, M. E. (2014) Handbooks for the Identification of British Insects Vol 6 part 6 The vespoid wasps (Tiphiidae, Mutillidae, Sapygidae, Scoliidae and Vespidae) of the British Isles. Royal Entomological Society
Day, M. C. (1988) Handbooks for the Identification of British Insects Vol 6 part 4. Spider wasps Hymenoptera: Pompilidae available as a free download
Morgan, D. (1984) Handbooks for the Identification of British Insects Vol 6 part 5. Cuckoo wasps Hymenoptera, Chrysididae available as a free download
Richards, O. W. (1980) Handbooks for the Identification of British Insects Vol 6 part 3b Scolioidea, Vespoidea and Sphecoidea Hymenoptera, Aculeata. Royal Entomological Society available as a free download
Yeo, P. F. & Corbet, S. A. (1983) Naturalists' Handbooks 3 Solitary wasps. Richmond Publishing