Reproductive Differentiation of Trichogramma pretiosum, T. semifumatumT. minutum, and T. evanescens, with Notes on the Geographical Distribution of T. pretiosum in the Southwestern United States and in Mexico (Hymenoptera: Trichogrammatidae)

Abstract

The reproductive compatibility of Trichogramma sp. (reference stock), T. semifumatum Perkins, T. minutum Riley, and T. evanescens Westwood, was investigated by a series of crossbreeding studies. No attempt was made to cross T. minutum and T. semifumatum . Eggs of the Mediterranean flour moth, Anagasta kuchniella (Zeller), were used as the host in the studies involving Trichogramma sp. and T. semifumatum . Eggs of the cabbage looper, Trichoplusia ni (Hubner), were used for the others. F1 females were not produced in any of the crosses or reciprocal crosses, indicating reproductive isolation and, therefore, that each species was a distinct species. Hereafter, the reference stock Trichogramma sp., reared from eggs of the bollworm, Heliothis zea (Boddie) collected from tomato in southern California, will be called T. pretiosum Riley. T. pretiosum readily crossed with a species of Trichogramma reared from parasitized H. zea eggs collected in Mexico from cotton and maize from Los Mochis, and from the same host on maize in Tehuacan, and Tapachula. The species of Trichogramma from Los Mochis readily crossed with one reared from parasitized eggs of the alfalfa caterpillar, Colias eurytheme Boisduval, collected from alfalfa near Calexico, California. A reference stock culture of T. pretiosum is available for additional studies to further define its range.