Date of Award
Doctor of Philosophy
Zoology and Genetics
Kenneth C. Shaw
The sounds of Amblycorypha parvipennis Stal katydid males consist of sequences of 4-5 s phrases consisting of an average of 24 phonatomes (20-25°C). Phonatomes consisting of 3-4 pulse trains generated during a single wingstroke, were produced at average rates of 4.5-5.5/s. Adjacent singing males alternate and overlap phrases and, where phrases overlap, phonatomes are synchronized. A. parvipennis females produce ticks which fall between male phonatomes. Trials in which paired chorusing males were recorded at intermale distances of 3.3 m and 40 cm with and without a ticking female present revealed that female presence elicited an increase in phrase rate and overlap and a decrease in phrase interval. In contrast, shortening the distance between males in the absence of a female elicited a reduction in phrase rate and overlap and an increase in phrase interval. The increase in phrase interval and reduction in phrase overlap when males are moved closer together in the absence of a female is explained by enhanced inhibition that the phrase of one katydid has on the phrase production of his chorusing partner. The increase in phrase rate and phrase overlap in the presence of a female may be a byproduct of the two males competing acoustically for the female or as indicated in a study on male competition, for a singing site. Another study involving two-choice discrimination tests, demonstrated that females moved to louder males and males that produced longer phrases, and that females tick more in response to the male they eventually move toward. A further study involving two-choice discrimination tests using computer-generated male calls also demonstrated female preference for loud calls, calls having long phrases, and calls containing phrases that did not overlap the ends of other phrases. It was also shown that females prefer phrase beginnings to endings and prefer phrases with fast phonatome rates similar to the rate at a phrase's beginning. Apparently, singing males compete to avoid overlapping the portion of their phrase that is most attractive to the female. The roles of the above male and female acoustic attributes in sexual selection are discussed.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Patrick LeRoy Galliart
Galliart, Patrick LeRoy, "The acoustic behavior of the katydid Amblycorypha parvipennis and the function of acoustic interaction in sexual selection " (1993). Retrospective Theses and Dissertations. 10232.