Sphecius convallis

Taxonomy

Order: Hymenoptera
Family: Crabronidae
Subfamily: Bembicinae
Tribe: Gorytini
Genus: Sphecius Dahlbom, 1844
Species: Sphecius convallis Patton, 1879
Common name: Pacific cicada killer

Background

Sphecius convallis, the Pacific cicada killer, is a species of solitary wasp in the family Crabronidae. It is found in Central and North America. Little is known about the biology of this species, but what we do know was covered by Coelho et al. (2020). The taxonomy has been treated by Holliday and Coelho (2006). It shares a lot of the same biology as the western cicada killer (S. speciosus). This species can sting, but it is not aggressive. They use their venom to paralyze cicadas to take back to their nests and feed their young.

How to separate from Asian giant hornet

  • Cicada killers can be as large or larger than Asian giant hornets and are frequently confused with AGH
  • The head is smaller in proportion to the body than AGH and the eyes are round (instead of notched)
  • This species is dark orange/red with yellow markings

Distribution

Sphecius convallis is endemic to Central America, Mexico, and the western United States. It is found at lower elevations than Sphecius grandis.

Distribution map of Sphecius convallis by GBIF: https://www.gbif.org/species/7623523

Diagnostic characteristics

  • Body length is 3–4 cm
  • The body is reddish-brown with yellow markings
  • The wing membrane is amber-tinted
  • Punctation is less dense in the middle of metasomal tergum 2, than on tergum 1, unlike the similarly colored S. grandis, where the punctation density is approximately equal
  • Flagellomeres II–IV are not curved ventrally and appear cylindrical

Diversity

There are 4 species of Sphecius in North America and 21 species worldwide. The genus occurs in Africa, Eurasia, and North and Central America.

Host/prey associations

Although adult cicada killer wasps feed on nectar from flowers, female cicada killers prey on cicadas to feed their larvae. A female captures and paralyzes a cicada by stinging it in the abdominal region, and then drags the paralyzed cicada into her underground nest where it is stored as food for the larvae (Drees and Jackman 1998, Milne and Milne 1980).

Nesting and general behavior

In general, cicada killers build their nests in the ground and often form nest aggregations that can contain large numbers of nests. Each nest is provisioned by a single female (Hastings et al. 2008). The nests are built in well-drained, exposed sandy soil, and the nest entrances are generally located in full sun. A female lays an egg in the body of a cicada and places the cicada in a nest cell. The larva emerges several days later and feeds on the cicada’s body for several weeks. In the fall, the larva spins a cocoon and pupates during the winter. It emerges from the pupal stage in early to mid-summer as an adult.

<p><em>Sphecius convallis</em>; photo by Donna Pomeroy, iNaturalist</p>
<p><em>Sphecius convallis</em>; photo by shirleysekarajasingham, iNaturalist</p>
<p><em>Sphecius convallis</em>; photo by Dylan Winkler, iNaturalist</p>
<p><em>Sphecius convallis</em>, dorsal view; photo by Todd Gilligan, USDA APHIS PPQ ITP</p>
<p><em>Sphecius convallis</em>, lateral view; photo by Todd Gilligan, USDA APHIS PPQ ITP</p>
<p><em>Sphecius convallis</em>, anterior view; photo by Todd Gilligan, USDA APHIS PPQ ITP</p>
<p><em>Sphecius convallis</em> (left) compared to <em>Vespa mandarinia</em> (right), dorsal view; photos by Hanna Royals and Todd Gilligan, USDA APHIS PPQ ITP</p>
<p><em>Sphecius convallis</em> face (left) compared to <em>Vespa mandarinia</em> face (right), anterior view; photos by Hanna Royals and Todd Gilligan, USDA APHIS PPQ ITP</p>