Western Cicada-killer Wasp

Pronunciation

How to pronounce Sphecius grandis: //ˈsfiːsiəs ˈɡrændɪs//

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Summary

Sphecius grandis, known as the western cicada killer, is a non-aggressive wasp species that preys on cicadas to provision its nests. It exhibits a yearly brood cycle, nesting behavior in aggregations, and distinct morphological traits that distinguish it from similar species. Males emerge earlier than females and are territorial during the mating season.

Physical Characteristics

Ranging in size from 3 to 5 cm (1 to 2 in) in length; amber-yellow body with yellow rings on its abdomen; females have punctation density in the middle of T1 and T2 that is about the same in S. grandis; males have antennomeres II–IV curved ventrally and appear bead-like. Females are heavier than males.

Identification Tips

Females of S. grandis can be distinguished from S. convallis by the coloration pattern of the gastral tergites and the density of punctation on the first and second tergites. S. grandis typically has yellow markings from first to fifth tergites, whereas S. convallis displays fewer marks in most specimens.

Habitat

Nesting aggregations found in bare sandy soil in full sunlight, often under sidewalks and in areas with little vegetation.

Distribution

Found in Central America, Mexico and the Western United States, from Washington and California to Nebraska and Texas, typically above 600 m elevation.

Diet

Primarily feeds on cicadas, especially Tibicen duryi, Tibicen dealbata, and Tibicen parallela. Females drag back paralysed cicadas to nest for their larvae to consume.

Life Cycle

The larvae hatch and feed on the cicadas provisioned by the female. Males generally emerge before females, with both genders mating between July and early August.

Reproduction

Females mate shortly after emergence and lay eggs in brood cells containing provisions of cicadas.

Ecosystem Role

Acts as a predator of cicadas, helping to regulate cicada populations in its habitat.

Economic Impact

Generally considered harmless to humans and not a pest; however, their nesting in gardens may lead to unwanted interactions.

Health Concerns

Stings vary from numbing to sharp but are considered non-lethal; males can be more aggressive than females.

Evolution

There are indications that S. grandis may represent multiple species as diverging clades have been suggested by mitochondrial DNA analysis.

Similar Taxa

• Sphecius speciosus
• Sphecius convallis
• Sphecius hogardii
• Sphecius spectabilis

Misconceptions

Often mistaken for being aggressive towards humans, when in fact they are rarely defensive unless provoked.

Tags

• wasp
• cicada killer
• Sphecius grandis
• Hymenoptera
• non-aggressive