
Of the 13,789 insects counted, only 31 were biting flies (a mere 0.22%!). Nearly half of the insects collected were nonbiting aquatic insects such as caddisflies and midges. More importantly, 1,868 predators and parasites (13.5%) were destroyed within 27 families of predators and nine families of parasitoids. Ground beetles, rove beetles, and braconid wasps were particularly common vicitms.
By their calculations, 71 to 350 billion nontarget insects are needlessly destroyed in the U.S. each year by misinformed homeowners, without any real control of nuisance insects. The heavy toll on nontarget insects, including beneficial insects, suggests that electrified traps may actually be counterproductive for insect control.
Source: Frick, T. B. and D. W. Tallamy. 1996. Density and diversity of nontarget insects killed by suburban electric
insect traps. Ent. News 107(2): 77-82.