Date of Award

Spring 1989

Document Type


Degree Name

Doctor of Philosophy (PhD)


Biological Sciences


Ecological Sciences

Committee Director

Daniel E. Sonenshine

Committee Member

Keith A. Carson

Committee Member

Roy L. Williams


Neutering of part-fed females virtually eliminated copulatory behavior in Dermacentor variabilis and D. andersoni males. Extracts from the anterior reproductive tracts (ART) of part-fed (7 days) females restored the male copulatory behavior in conspecific neutered females, suggesting the presence of a genital sex pheromone (GSP). Similar extracts from unfed females did not restore the behavior, suggesting that the pheromone was produced during feeding. Perception of the GSP by sensillae on the male cheliceral digits was confirmed by electrophysiological techniques.

Ecdysteroids, specifically ecdysone and 20-OH-ecdysone were shown to be present in the anterior reproductive tracts in excess of amounts that could be explained by mere hemolymph contamination. Ecdysteroids were also found in washings of the vaginal lumen of these two species. D. andersoni females contained larger amounts of ecdysteroids than D. variabilis females. Males of D. variabilis and D. andersoni responded positively to authentic ecdysone, and 20-OH-ecdysone in neutered female bioassays and electrophysiological assays. The strongest responses were to 20-OH-ecdysone in both species. No response was found with sterols. 20-OH-ecdysone and possibly ecdysone appear to be components of the genital sex pheromone (GSP) of D. variabilis and D. andersoni. Species recognition is facilitated by these components, but the complete mechanism is not yet fully understood. The importance of ecdysteroids in the evolutionary development of chemical communication systems in Arthropoda is also discussed.


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