Differences in Female Calling Behavior of Three Interfertile Sibling Species of Euxoa (Lepidoptera: Noctuidae)1

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Abstract
The calling behavior of 3 closely related, interfertile species of cutworm moths, E. declarata (Walker), E. campestris (Grote), and E. rockburnei Hardwick, was studied in the laboratory. The temporal pattern of calling activity by virgin females differs for each species with a peak of calling in scotophase at 2.3 h for declarata, 7.7 h for campestris, and 10.3 h for rockburnei. The calling period of declarata is exclusive from that of rockburnei and nearly exclusive from that of campestris. There is overlap between the calling periods of campestris and rockburnei but the initial and peak phases, which under natural conditions with males present would be by far the most important, are separated by 2.5 h. Differences in calling rhythm are probably sufficient to account for the strong conspecific mating tendency exhibited by these species in laboratory tests, although such differences may not be the only isolating mechanism involved.