HILL, R.I.*; VACA, J.F.; Univ. of California, Berkeley: Differential Wing Strength In Pierella Butterflies (Nymphalidae, Satyrinae) Supports The Deflection Hypothesis

The �deflection hypothesis� asserts that conspicuous marginal patches on insect wings function to deflect predator attacks to these patches and away from more vital body parts. As a result of selection from such predator attacks these marks are predicted to be relatively weak and thereby increase probability of escape. To test this prediction, hindwing-tear weight (an estimate of wing strength) was measured for three species of Pierella butterfly (Nymphalidae, Satyrinae) differing in the presence of a conspicuous hindwing tornus patch. Pierella astyoche, the species with a conspicuous white hindwing patch was found to have significantly lower tear weight than P. lamia and P. lena, two species lacking such a patch. Body size was not found to be an important factor explaining variation in wing-tear weight. However, a positive relationship between insect age and tear weight was found. For P. lamia and P. lena the data suggest older individuals have higher tear weight whereas this relationship is absent in P. astyoche. These results represent the first direct support for the prediction that deflection marks are especially designed to break away easily, and support the hypothesis that the white patch in Pierella astyoche functions as a deflection mark.