Sphecius speciosus, the eastern cicada-killer wasp, is a large, solitary digger wasp species in the family Bembicidae. They are so named because they hunt cicadas and provision their nests with them. Cicada killers exert a measure of natural control on cicada populations, and as such, they may directly benefit the deciduous trees upon which the cicadas feed. Sometimes, they are erroneously called sand hornets, despite not truly being hornets, which belong to the family Vespidae.

The most recent review of this species' biology is found in the posthumously published comprehensive study by noted entomologist Howard Ensign Evans.

Distribution

This species can be found in the Eastern and Midwest U.S. and southwards into Mexico and Central America.

Description

thumb|left|Five female eastern cicada killers, Sphecius speciosus

Adult eastern cicada wasps are large, long, robust wasps with hairy, reddish, and black areas on their thoraces (middle parts), and black to reddish brown abdominal (rear) segments that are marked with light yellow stripes. The wings are brownish. Coloration superficially resembles that of some yellowjacket and hornet species. The females are somewhat larger than the males, and both are among the largest wasps seen in the Eastern United States, their unusual size giving them a uniquely fearsome appearance. European hornets (Vespa crabro) are often mistaken for eastern cicada killers, though at about long, they are smaller than the largest cicada killers. The males are smaller than the females because they are not given as much larval food; since females must carry the cicadas they have killed to a burrow for nesting, they benefit from being larger, and are given more food as larvae.

thumb|Male eastern cicada killer perched on a [[Rudbeckia hirta|black-eyed susan to defend its territory]]

Life cycle and habits

left|thumb|A female S. speciosus digging a burrow next to a driveway

left|thumb|upright|Eastern cicada-killer wasp holding a paralyzed cicada at [[John Heinz National Wildlife Refuge]]

Solitary wasps like the eastern cicada killer are very different in their behavior from the social wasps such as hornets, yellowjackets, or paper wasps. Cicada killer females use their stings to paralyze their prey (cicadas) rather than to defend their nests; unlike most social wasps and bees, they do not attempt to sting unless handled roughly. Adults feed on flower nectar and other plant sap exudates. They are present in a given area for 60 to 75 days, usually until mid-September. Males emerge first to compete for females. The large females are commonly seen skimming around lawns seeking good sites to dig burrows and searching for cicadas in trees and taller shrubs. In digging a burrow, the female dislodges the soil with her jaws, and using her hind legs, pushes loose soil behind her as she backs out of the burrow. Her hind legs are equipped with special spines that help her push the soil behind her. The excess soil pushed out of the burrow forms a mound with a trench through it at the burrow entrance. Cicada killers may nest in planters, window boxes, or flower beds, or under shrubs, ground cover, etc. Nests often are made in the full sun where vegetation is sparse. Males aggressively defend their perching areas on nesting sites against rival males, but they have no stinger. Although they appear to attack anything that moves near their territories, male cicada killers are actually investigating anything that might be a female cicada killer ready to mate. Such close inspection appears to many people to be an attack, but male and female cicada killers do not land on people with the intent to sting. If handled roughly, females will sting, and males will jab with a sharp spine on the tip of their abdomen. They are generally not aggressive towards humans and usually fly away when swatted at, rather than attacking.

Sphecius spectabilis <small>(Taschenberg, 1875)</small>, is found in the South American countries of Argentina, Bolivia, Brazil, Chile, Colombia, French Guiana, Paraguay, Surinam, and Venezuela.

Sixteen other cicada-killer wasp species in the genus Sphecius are found in Europe, the Middle East, Africa, and Asia. Other genera of cicada-killing wasps (e.g., Liogorytes in South America and Exeirus in Australia) are the "cicada killers" of their native lands.

References

  • Sphecius, a comprehensive list of taxonomic information on the genus.
  • Dick Walton's Solitary Wasps Page, with video clips of Sphecius speciosus and other digger wasps
  • Eastern cicada killer, on the University of Florida / Institute of Food and Agricultural Sciences Featured Creatures website
  • A fact sheet from the Ohio State University Extension