Abstract
The mating behavior of Thrips nigropilosus, which consists of arrhenotokous and thelytokous populations, was studied under laboratory conditions. The variation in esterase isozymes of individual adult females from a thelytokous population and seven arrhenotokous populations was analyzed by polyacrylamide gel electrophoresis. Mating occurred between individuals of arrhenotokous populations from different localities. Although males of an arrhenotokous population approached and attempted to copulate with females of a thelytokous population from the same locality, the thelytokous females never accepted the arrhenotokous males. The arrhenotokous populations showed high variability in esterase zymograms, but the thelytokous population had no variation in zymograms. Females reproducing thelytokously and arrhenotokously could be discriminated from each other based on their zymograms. We conclude that arrhenotokous and thelytokous populations should be treated as separate species.