Based on our studies with 10 geographic populations of Chrysopa carnea, we recommend that biological control programs involving this predator use "pure" carnea stock originating from eastern and midwestern North America. Of the two strains (races or biotypes) of C. carnea—carnea and mohave—carnea is the superior choice for biological control on commercial crops in both eastern and western North America because (1) its preoviposition period is approximately one-half as long as mohave’s, (2) unlike mohave adults, neither sex of the carnea strain requires prey for successful mating and initiating oviposition, (3) carnea’s oviposition can be enhanced in the field by applying currently available food sprays, and (4) carnea is efficient to mass-rear on a commercial basis.
The “pure” mohave race is restricted to limited areas on the west coast. This race, which can enter a food-mediated summer diapause, is more suitable for biological control on the west coast in non-agricultural situations dominated by native vegetation, where prey occurrence is highly variable during summer.
Most west coast populations in agricultural areas are composed of intermediates between the carnea and mohave races. F1 hybrids produced by crossing individuals from mohave, carnea, and intermediate populations, show predominantly carnea characteristics, and inheritance of the distinguishing biological traits appears to be controlled by polygenes.