1974] 
Eisner et al. — Tenebrionid Beetles 
205 
ing. It seems clear, however, that the chirps are of sufficiently broad 
frequency composition to be at least potentially audible to virtually 
any acoustically sensitive predator. 
Summary 
The black flightless tenebrionid beetles Adelium percatum and A. 
pustulosum from Australia possess a pair of eversible abdominal 
glands that secrete a mixture of 2-methyl- 1,4-benzoquinone, 2,3- 
dimethyl-i,4-benzoquinone, and i-pentadecene. The tubular glands 
are unusually large, and when everted may be nearly half as long as 
the beetles themselves. In A. percatum , the replete glands may, on 
extrusion, spray their contents forcibly, to a recorded maximum dis- 
tance of 25 cm. Defensive administration of secretion is also effected 
by the beetles’ legs. A. pustulosum , unlike A. percatum , produces an 
audible “disturbance sound” when molested. The sound is engendered 
by the scraping of two serrated ridges on the last abdominal tergum 
across the elytral margins. The morphology of the stridulatory ap- 
paratus, and the acoustical properties of the sound, which contains 
frequencies ranging from below 1 kHz to 60 kHz, are presented. It 
is argued that disturbance sounds, when produced by chemically or 
otherwise protected animals, act as acoustical aposematic signals, 
operative primarily in darkness. 
Acknowledgements 
We thank the staff of the Division of Entomology, C.S.I.R.O., for 
much help and hospitality during the Eisners’ stay in Canberra. The 
beetles, which were first shown to us in the field by Dart Linsley, 
were identified by E. B. Britton. Electronmicrographs were made at 
the laboratories of Barry Filshie, Colin Beaton, and Margaret 
Kovaks, who were most generous with time and facilities. Robert 
Capranica provided acoustical equipment and technical advice. The 
study was supported in part by Grant AI-02908 from the National 
Institutes of Health, and was carried out while T. Eisner was a 
John Simon Guggenheim Memorial Foundation Fellow. 
References Cited 
Alexander, R. D. 
1967. Acoustical communication in arthropods. Annual Rev. Entomoh 
12: 495-526. 
