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Promachus giganteus - female

Promachus giganteus - Female
El Paso, approx. 32 miles East - gravel, tar bush community, Hueco Mtns, El Paso County, Texas, USA
June 23, 1991
Size: 34 - 46+ mm
Promachus giganteus, one of the largest species of North American robber flies, is quite common in New Mexico and West Texas throughout the month of June and sometimes as late as August. Sufficient rainfall is required to support a large population. Their prey includes large grasshoppers, cicadas, the largest Xylocopa, male Pepsis wasps and other large robber flies. Females frequently exceed 40mm in body length, with occasional giants exceeding 46mm. The wings of giganteus are proportionately longer than those of other Promachus. Though frequently mistaken, even by entomologists, for the large form of P. nigrialbus from central Arizona, giganteus can be separated by the mixture of gray pollen into the black abdominal bands, ovipositor beginning with segment six, sparse black spination dorsally on the femurs (appearing gray from a distance - those of nigrialbus appear nearly black) and larger size (though some nigrialbus individuals overlap small giganteus in length).

Images of this individual: tag all
Promachus giganteus - female Promachus giganteus - female


Moved from ID Request.

great info
Awesome natural history lesson. thanks. would this species be found in Illinois? Have found robbers that size patrolling sand bars along rivers and streams for prey.

Promachus giganteus range
In North America Promachus giganteus is found only in the arid desert regions of western Texas, southern New Mexico and in a small pocket north of Portal, Arizona. I have found them perched near and on the narrow trunks of desert willow in dry washes, menacing carpenter bee visitors to the fragrant blooms. Often they are found on creosote.

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