We have continued to study the sexual selective strategy of Utetheisa ornatrix, an arctiid moth that depends on defensive pyrrolizidine alkaloids for survival. The moth obtains the alkaloid as a larva from its foodplant, and retains it through metamorphosis into the adult stage. The adult female transmits alkaloid to the egg, as a result of which she incurs an alkaloid deficit. She makes up for this shortfall by mating with numbers of males, which transmit alkaloid to her with the sperm package. The female mates preferentially with larger males, which bestow large alkaloidal gifts. Body size is a heritable trait in Utetheisa, as the result of which the female, by choosing larger males, begets larger sons and daughters. These are respectively more successful in courtship, and more fecund. Therefore, by being discretionary in her choice of mate, the female is enabled to receive large alkaloidal gifts, and genes that provide for increased fitness of her offspring. Utetheisa has proven to be an ideal experimental animal, and we remain committed to its further study.

We have completed our study of one of Archbold's more endearing insects, the iridescent blue chrysomelid beetle, Hemisphaerota cyanea (see photo, this page). We have elucidated the mechanisms by which the adults secure foot adhesion for defense, a mechanism that involves committing all their 60,000 tarsal bristles to contact with the substrate. The bristle tips are wetted by an oil, which serves as the adhesive. We have succeeded in identifying the chemicals that make up the oil, the first time that this has been achieved for tarsal adhesives in insects. In addition, we completed a study on the larva of Hemisphaerota, which protects itself by way of a dorsal shield, constructed from fecal strands.

Project Director: William E. Conner, Wake Forest University
Outside Collaborators: Thomas Eisner and Frank Schroeder, Cornell University
Graduate Students: Nickolay Hristov and Reed Johnson, Wake Forest University

Another arctiid moth Cosmosoma myrodora provides an interesting contrast to Utetheisa (described above). Only male Cosmosoma collect pyrrolizidine alkaloids and they do so as adults. They acquire the alkaloids by nocturnal visitation at dogfennel, Eupatorium capillifolium, and its relatives. Males regurgitate on the plant and reimbibe an extract rich in surface alkaloids. An aliquot of the alkaloids is quickly transferred to flocculent-filled pouches on the venter of the insect and to the male reproductive tract. During courtship male Cosmosoma shower (see photo, this page) the female with flocculent providing her with an instantaneous defense in the form of an alkaloidal shield. During copulation the male transfers additional alkaloids to the female in a spermatophore. Whether females choose mates based on their ability to provide alkaloid is an open question that we hope to address.