PROC. ENTOMOL. SOC. WASH. 88(1), 1986, pp. 25-29 RESPONSE OF GERMAN COCKROACHES TO A DISPERSANT AND OTHER SUBSTANCES SECRETED BY CROWDED ADULTS AND NYMPHS (BLATTODEA: BLATTELLIDAE) Mary H. Ross and Keith R. Tignor Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061. Abstract. — The responses of adult male German cockroaches to filter papers conditioned by crowded adult males and by large nymphs is compared to their response to female-conditioned papers. Males were repelled only from the latter papers. The lack of repellency to papers conditioned by males and large nymphs may be attributed to insufficient amounts of a dispersant pheromone to counteract the response to aggregation pheromone. Chemical cues mediate defensive, reproductive, and social behaviors in insects. For example, aggregations are pheromonally induced in the crickets Ceuthophilus secretus (Nagel and Cade, 1983), Acheta domestica (Sexton and Hess, 1968; McFarlane et al., 1983), locusts (Gillett, 1968) and the cockroach, Blattella ger-manica (L.) (Bell et al., 1972; Ishii, 1970; Ishii and Kuwahara, 1967; Rust and Appel, 1985). In A. domestica (Sexton et al., 1968) and B. germanica (Suto and Kumada, 1981), the response to aggregation pheromone is countered by repellent effects of a dispersant which, in A. domestica, is secreted by both adult males and females. In B. germanica the dispersant was detected in bioassays where filter paper was conditioned by crowding adults of both sexes. Further study indicated the dispersant is present in oral secretions and is probably a proteinaceous sub-stance^) (Nakayama et al., 1984). Nymphs of all stages, adult males, and gravid and non-gravid females were repelled from papers conditioned by crowded adult females, indicating all mem-bers of a population would respond to the dispersant (Ross and Tignor, 1985). The purpose of the present experiment was to determine whether cockroaches would also be repelled from papers conditioned by crowded adult males or large nymphs and to compare the response to that from female-conditioned papers. Adult males were used to test for repellency because they showed a particularly strong response to female-conditioned papers (Ross and Tignor, 1985). Materials and Methods Cockroaches were drawn from the VPI wild-type strain. It has been maintained in our laboratory for approximately 160 generations. The laboratory is on a 14D/ 10L photocycle with temperature range of 24-2 7°C. Our bioassay technique was patterned after that of Ishii et al. (1967) and Suto and Kumada (1981). It differed from the experimental design we used to test response of different age/sex classes
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