Journal of Chemical Ecology. Vol. 22. No. 2. 1996 CONTRASTING REACTIONS OF LOGGERHEAD SHRIKES TO TWO TYPES OF CHEMICALLY DEFENDED INSECT PREY t REUVEN YOSEF, 2 JAMES E. CARREL, 3 and THOMAS EISNER 4"* "-htternational Birdwatching Center P.O. Box 774, Eilat 88000 Israel ~Division (~"Biological Sciences 106 Tucker Hall, University of Missouri-Columbia Columbia~ Missouri 65211 aSection of Neurohiology attd Behavior Came// Universi O' Ithaca, New York 14853-2702 (Received October 27. 1994; accepted September 25, 1995) Abstract--Feeding tests with loggerhead shrikes ~lxmius huh~vicianus) showed this bird to accept Utetheixa at'tlalrix, a moth (Arctiidae) protected by pyr- rolizidine alkaloids, but to avoid Lytta polila, a beetle (Meloidae) containing cantharidin. Key Words--Arctiidae, Meloidae, Utetheisa ornatrix, Lytta polita, pyrroli- zidine alkaloids, cantharidin, feeding aversion. I NTRODUCTION The moth Utetheisa ornatrix (family Arctiidae) and the beetle Lytta polita (fam- ily Meloidae) are both chemically protected, the former by pyrrolizidine alka- loids (PAs) sequestered from the larval food plant (Eisner and Meinwald, 1995), the latter by cantharidin, produced by the beetle itself (McCormick and Carrel, 1987). We recently undertook some feeding tests with loggerhead shrikes (Lan- ius ludovicianus, family Laniidae), in the expectation that the birds would reject both these insects, but found that they spumed L, polita only, and fed readily *To whom correspondence should be addressed. ~Paper no. 130 of the series Defense Mechanisms of Arthropods; no. 129 is T. Eisner and J. Meinwald, Proc. Natl, Acad. Sci. U.S.A. 92:50-55, 1995. 173 0Oq8 0331/96/0200-0 i73 $0950•0 E~, 1906 Plenum Publishing Ctwp~litm