i960] 
Eisner — Defense Mechanisms 
69 
natorial effectiveness of an arthropod’s secretion against a vertebrate, 
long-term feeding experiments should be made, to test for any dis- 
criminatory tendencies that might eventually develop after a greater 
number of encounters, and particularly in situations where the pre- 
dator is also given palatable insects as an alternative choice. 
With Hyla the results were different. Five of the eleven earwigs 
offered (over a period of a few hours) were caught and swallowed, 
but the rest were promptly spat out (there was no apparent order in 
the sequence in which the earwigs were either taken or rejected). 
Whether rejection was on the basis of the secretion alone, or was also 
attributable to trauma induced by the pincers, could not be deter- 
mined. That the secretion may in itself be repellent is suggested by 
the fact that benzoquinones are strongly irritating when applied topic- 
ally to an amphibian : a mere sprinkling of a few crystals of p- benzo- 
quinone on Hyla invariably elicits a prompt scratch reflex. The pin- 
cers may also be of importance, however. In one instance a frog had 
difficulty rejecting an earwig, which was seen to have become firmly 
clamped to its tongue, and which was not removed until the frog used 
its forelegs to brush it away. 
Acknowledgements : I am indebted to Professor Carrol M. Williams 
of Harvard University, and also to his family, for having collected 
the earwigs for me, and to Professor Edward O. Wilson for use of 
his Pogonomyrmex colonies at Harvard. Thanks are also due Profes- 
sor Kenneth D. Roeder, Tufts University, who made the mantids 
available at his laboratory, and Dr. J. A. G. Rehn who identified 
them. Dr. Hermann Schildknecht, University of Erlangen, Germany, 
was kind enough to let me see his manuscript (Schildknecht and Weis, 
i960) before its appearance in print. 
References Cited 
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1961, The effectiveness of arthropod defensive secretions. Proc. 
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