ORDER: Hymenoptera FAMILY: Sphecidae GENUS: Sphecius SPECIES: speciosus
Description: Cicada Killers are large wasps, approximately two inches in length. They are black or dark brown, with colorful yellow markings on several segments of their abdomen. Their wings are amber.
Distribution: Cicada Killers (Sphecius speciosus) are present in the eastern United States, east of the Rocky Mountains. There are a handful of species in the genus Sphecius within the United States, and a species in the western United States, known as Sphecius convallis, is termed the Western Cicada Killer. It is the largest wasp in California. Cicada Killers appear as adults in late June or July, and are mostly seen visiting flowers or digging burrows in sandy or light soil. In Washington, D.C., they are commonly seen in July on the National Mall.
Life cycle: This species nests in the ground and provisions its nest with cicadas. As in many insect species, the males appear as adults first, and mating takes place when adult females emerge from the soil. After mating, females select a site and begin digging a burrow. Favorite sites are embankments, under sidewalks and roadsides. Commonly, lawns are chosen in populated areas. Soil or sand is first loosened with the front legs, then scooted out of the hole with her middle and hind legs. Sometimes the female enters the burrow and pushes out soil with her head and front legs. Females burrow into the soil for approximately ten inches, with a channel of about half an inch. Oval chambers are excavated at the end of the burrow, large enough to accommodate a few individual cicadas. The female then seeks a cicada in the trees, apparently by vision rather than sound, suggested because the majority of her prey are female cicadas which make no sound. Cicadas are usually captured in flight. Cicadas are paralyzed by the venom of the wasp's sting, and will remain alive during the feeding of the wasp larvae. After stinging the cicada, the female wasp carries it back to her burrow, sometimes a hundred yards away. She sometimes uses the law of physics by climbing a tree or shrub and partly gliding with the cicada in the direction of her burrow. Without the presence of trees or shrubs, she will walk on the ground. The female Cicada Killer lays one egg in a cell with one, two or three cicadas, then seals the chamber. Cicada Killers adhere to the normal pattern of solitary wasps by mass provisioning their brood cell. The cells are prepared and completed one by one. Enough food is provided in the cell for the larva to survive until pupation. Rarely solitary wasps engage in progressive provisioning, which involves caring for several cells at one time and adding food daily to each cell during the growth of the larvae. The eggs of the Cicada Killer hatch in two or three days, producing larvae that feed for about two weeks, which then spin a cocoon of silk mixed with sand or soil. The pupal case is held in the center of the cell by silk strands, and the cocoons remain in the chamber through the winter, with emergence as adults in the following summer.
Damage done. Cicada Killer Wasps are solitary wasps, but can occur in such numbers that they disturb lawns with their burrows. They also will sting if molested. They are considered a minor pest. Their value in the food chain arguably outweighs their "bad side." Researcher Arnold Menke of the Systematic Entomology Lab, U. S. Department of Agriculture, was strongly irritated in 1993 to find scores of adults of Cicada Killers dead on the sidewalk due to insecticide spraying of trees outside the National Museum of Natural History.
SELECTED REFERENCES:
Dambach, C. A. and Good, E. 1943. Life history and habits of the cicada killer in Ohio. The Ohio Journal of Science, Volume 43.
Davis, W. T. 1921. Mating habits of Sphecius speciosus, the cicada-killing wasp. Bull. Brooklyn Ent. Soc., Volume 15: 128-129.
Dow, Richard. 1942. The Relation of the Prey of Sphecius speciosus to the Size and Sex of the Adult Wasp (Hym.: Sphecidae). Annals of the Entomological Society of America, Volume 35: 310-317.
1999
