Sexual selection in the spotted cucumber beetle, Diabrotica undecimpunctata howardi (Coleoptera: Chrysomelidae) male traits favored by cryptic female choice /

by Darlington, Mark Burton.

In the spotted cucumber beetle Diabrotica undecimpunctata howardi (Coleoptera: Chrysomelidae), the female determines the final outcome of mating; internal muscle control allows her the capability of blocking the transfer of sperm from the male. Males respond to this “cryptic female choice” by rhythmically stroking the female with their antennae in a distinctive pattern. The rate of this “antennation” is the best known predictor of a successful outcome for the mating, males that have a higher antennation rate are more likely to pass a spermatophore to the female. I examined a number of male traits testing for correlations with antennal stroking behavior, and found two significant results: (1) Antennation rates increased in captivity despite very high levels of artificially induced inbreeding, the opposite of expectation, probably due to heightened sexual selection for mating display rate. And (2) males with fast antennal stroking rates had a greater propensity to fly rather than run in a simulated escape test. Fieldwork indicated a high proportion of the beetles that appeared in squash fields early in the season were “flyers”, females may therefore prefer fast antennating males because they develop faster or because flight might confer an ecological advantage in foraging ability. iii