Robber flies have the potential to greatly affect populations of insects because they are strong fliers and efficient predators (Joern A. and Rudd N. 1982).

Their proboscis never elongate because they are adapted for piercing (Back E. 1909).

Difference in coloration between sexes is not very general among this species (Back E. 1909).

The difference in Promachus vertebratus and Promachus rufipes are not easily identified, but the deeper brown coloring in the latter species can help the determination (Williston S. W. 1885).

An abdomen with a broad black spot in front of each segment and on the sides densely yellowish and brownish coloring, followed by a deep reddish brown thorax help identify Promachus vertebratus (Williston S. W. 1885).

The average size of Promachus vertebratus is 26 to 31 millimeters, although larger ones have easily been recorded (Hines J. W. 1911).

Male genitalia are black with pale hair, while the female genitalia are shinning black (Hines J. W. 1911).

Most likely all species of Promachus will prey on the honeybee if given the chance (Bromley S. W. 1930).

Promachus vertebratus seem to prefer prey that "buzz" instead of "flutter", although they will definitely prey on grasshoppers (Bromley S. W. 1930).

The female lays its white, elliptical eggs in fall in little earthen cavities or cracks in the soil (Malloch J. R. 1922).

According to observation, the larva of Promachus vertebratus is the most common of the asilids to attack and feast on white grubs (Malloch J. R. 1922).

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