Sphecius grandis

(Say, 1823)

Western Cicada Killer, Western Cicada-killer Wasp

Sphecius grandis is a large, solitary to western North America, ranging from Central America through Mexico to the Western United States. Females construct burrows in sandy, well-drained soils, often forming nest with hundreds of individual nests. They provision underground with paralyzed cicadas (primarily Tibicen duryi, T. dealbata, and T. parallela) as food for their larvae. The exhibits pronounced : females are larger (forewing length 2.5–3 cm, mass ~256 mg) and live approximately one year, while smaller males (~95 mg) emerge earlier, live only a few days, and engage in aggressive territorial competition for mating access. Activity is concentrated in July and early August, synchronized with . Despite their large size and formidable appearance, they are not habitually aggressive toward humans.

Western CKs mating by Chuck Holliday. Used under a Public domain license.

American entomology (Plate 2) (6026021225) by Say, Thomas. Used under a Public domain license.

Pronunciation

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

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Identification

Most reliably distinguished from the sympatric Pacific Killer (S. convallis) by punctation on the first and second gastral tergites rather than color pattern alone. S. grandis typically shows yellow markings on tergites one through five (though variable), while S. convallis usually shows markings only on tergites one through three or four. The of S. grandis has pale bands extending along its entire length, whereas S. convallis bands terminate before the abdominal tip. Females possess heavy, blade-like spines on the hind tibia modified for digging; males have shorter, less conspicuous spines. Body length 3–5 cm; coloration amber-yellow with yellow abdominal rings and -black body hue; rufous spots present on first and second tergites.

Images

Habitat

Nests in well-drained, bare sandy soils in full sunlight, frequently under sidewalks, in backyards, gardens, and dry wash banks. Rarely found in vegetation-rich areas. Most commonly associated with riparian zones. Occurs at higher mean elevations than (average 755 m), ranging from low desert elevations to montane zones.

Distribution

to Central America, Mexico, and the Western United States. In the U.S., found from Kansas, Nebraska, and Oklahoma west through New Mexico, Texas, Nevada, California, Idaho, Oregon, and southeast Washington; absent from Wyoming. Mexican records include Baja California Norte, Baja California Sur, Coahuila, Nuevo León, Tamaulipas, and Yucatán. Also recorded from Nicaragua (Granada), Rica (Guanacaste), and Honduras. Co-occurs with S. speciosus and S. convallis at Big Bend National Park, Texas.

Seasonality

with , mating, and nesting concentrated in July and early August. Males emerge several days before females. Approximately 90% of life spent underground as larvae.

Diet

feed on nectar and tree sap; females provision nests exclusively with cicadas (Tibicen duryi, T. dealbata, T. parallela). Two or more cicadas placed per ; female cicadas preferred for greater consumable tissue, though males more frequently captured due to their conspicuous calling .

Host Associations

Tibicen duryi - preyprimary
Tibicen dealbata - preyprimary
Tibicen parallela - preyprimary
Cacama valvata - preycactus dodger , taken in Arizona

Life Cycle

Complete with solitary nesting. Female excavates burrow with U-shaped entrance mound, tunnel extending up to ~1 m depth with multiple lateral . Each cell provisioned with 1–4 paralyzed cicadas; single laid per cell. Larva feeds on tissue, overwinters in cell, pupates following spring. One cicada yields male ; two or more yield female. Approximately 90% of lifespan spent as subterranean larva.

Behavior

Females hunt cicadas in low tree trunks, guided by male calls; paralyze prey by stinging , then transport prey weighing ~88% of body mass back to nest. Capable of : maintains high, regulated temperature during territorial patrolling, with ability to transfer heat from thorax to . Males perch on elevated substrates (stumps, pebbles, wood, weeds, grass blades, low branches) overlooking female nest , defending territories through butting, grappling, and aerial carrying displays of rival males; larger and younger males generally . Males rarely perch on ground. Non-territorial mating tactics observed in smaller males, including delayed . Females mate once, with first male encountered, then reject subsequent advances.

Ecological Role

of cicadas; control of . contribute to pollination through nectar feeding. Subterranean larvae may influence soil structure through burrowing activity.

Human Relevance

Frequently encountered in urban and suburban environments due to nesting in bare soil areas, sidewalks, and gardens. Generally ignored by humans; females not aggressive and sting only if handled or stepped on. Sting reported as numbing to moderately painful despite large size. Males more aggressive but lack stingers. Pest control rarely warranted due to temporary nesting period (~1 month) and non-aggressive nature.

Similar Taxa

Sphecius convallisSympatric in western North America; distinguished reliably by punctation on first and second tergites rather than color pattern; S. convallis bands typically terminate before abdominal tip
Sphecius speciosusEastern with overlapping range in Texas; similar nesting and appearance, but in most of range
Sphecius hogardiiCaribbean ranging into southern Florida; distinguished by distribution and subtle morphological differences