A POSTINSEMINATION BARRIER TO FERTILIZATION ISOLATES 2 CLOSELY-RELATED GROUND CRICKETS

Postinsemination barriers to fertilization generally have been ignored by biologists interested in the origin and nature of reproductive iso lation among closely related terrestrial animals. Yet evidence present ed in this paper indicates that such a barrier bears primary responsib ility for the reproductive isolation between the ground crickets Allon emobius fasciatus and Allonemobius socius. Postinsemination barriers t o fertilization may isolate many other terrestrial animals as well, bu t the design of most laboratory hybridization experiments precludes th e detection of these barriers.