Courtship behavior of phycitid moths. II. Behavioral and pheromonal isolation of Plodia interpunctella and Cadra cautella in the laboratory

Interspecific courtship was observed between the Indian meal moth, Plodia interpunctella, and the almond moth, Cadra cautella. Successful cross-mating did not occur, however, because of the following isolation mechanisms: (1) incompatible courtship behavior, (2) male sex pheromone as a species recognition signal, (3) inhibition of males to female sex pheromone stimulation, and (4) mechanical or physiological barriers to insemination.Male Indian meal moths were strongly excited by calling almond moth females and courted them vigorously. However, because the courtship behavior of this combination was incompatible, copulation did not occur. Occasionally courtship continued to a later stage in the sequence but then the female rejected the male apparently because he releases an inappropriate aphrodisiac from his scent scales.In the reciprocal cross, fully two-thirds of the almond moth males failed to be sufficiently excited by Indian meal moth females to court them. Most of these males were inhibited, as indicated by their subsequent lack of response to pheromone extracts from their own female. Those males which were excited by Indian meal moth females courted them successfully and copulated, but insemination apparently did not occur. In a few cases the females rejected the males, as in the reverse cross.