PARENT SESSION
Oral Session # 99: Late-Breaking Newsworthy Presentations.
Presiding: E Preisser and G Larocque
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 205.

The scent of fear: Genetic and phenological contributions to variation in the osmeterial chemistry of tiger swallowtail larvae.

Frankfater, Cheryl^*,1, Tellez, Mario², Rimando, Agnes², Slattery, Marc¹, ¹ Department of Pharmacognosy and the National Center for the Development of Natural Products, University, MS, 38677² USDA-ARS Natural Products Utilization Research Unit, University, MS, 38677

ABSTRACT- Swallowtail butterfly caterpillars possess an eversible, two-pronged gland situated between the head capsule and the thorax, that they can protrude upon perceived predation threats. The glands glisten with an odiferous secretion thought to repel potential predators. We analyzed the secretion from individual tiger swallowtail caterpillars (Papilio glaucus) by sampling with solid phase microextraction fibers coupled to GC/MS. We followed the caterpillars from different broods reared on either black cherry or tulip tree leaves throughout all five larval stages, or instars. A mixture of many mono- and sesquiterpenes characterized the secretions of caterpillars of the first four instars, while 2 short chain fatty acids predominated the exudate of the fifth instar larvae. The chemistry of the early instars did not differ qualitatively but rather quantitatively. Of the 15 terpene peaks chosen for further analysis, we found that 13 showed statistically significant changes over time. A 2-way multivariate analysis of variance was used to determine the effects of genetics versus diet on the osmeterial profile (peak percentages) of third instar caterpillars. Nine peaks revealed a statistically significant maternal effect, while 2 were impacted by diet. Terpenes have been shown to repel a variety of invertebrate and vertebrate predators, and the response of different predators to the same compound often differs. Therefore, changes in the quantities of the terpene compounds over time may serve to make the growing larvae less vulnerable to larger predators, and maternal effects on the osmeterial profile may give certain lines a selective advantage depending on the predator fauna encountered during a particular season.

Key words: osmeteria, Papilio, defense, terpenes