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Psyche 
[March 
have defensive glands (e.g., Tentyriinae and Asidinae). But the 
glands are frequently present, and when they are, they are either 
exclusively abdominal as in Adelium , or supplemented by a second 
pair of glands in the prothorax (Roth, 1945; Tschinkel, 1969). 
Only relatively few tenebrionid secretions have been studied chem- 
ically. Most produce benzoquinones, including />-benzoquinone, and 
its alkylated derivatives 2 -methyl- 1,4-benzoquinone and 2-ethyl- 1,4- 
benzoquinone (references in Jacobson, 1966; Roth and Eisner, 1962; 
Weatherston, 1967; Weatherston and Percy, 1970). Naphthoqui- 
nones have been reported in one species (Tschinkel, 1972) and in 
another the prothoracic glands produce phenols instead of quinones 
(Tschinkel, 1969). 2, 3-Dimethyl- 1,4-benzoquinone itself has not 
been found in a tenebrionid secretion, but it is produced by the de- 
fensive glands of certain opilionids (Fieser and Ardao, 1956; Eisner 
et al.j 1971b). The presence of an alkene in Adelium is no novelty. 
Hydrocarbons, both saturated and unsaturated, are known from 
arthropod secretions, and although i-pentadecene as such has not been 
reported, shorter chain homologs of the substance are present in 
Tenebrionidae (Hurst et al., 1964). 
We made no effort to evaluate the defensive effectiveness of the 
secretion of Adelium. However, judging from the proven deterrency 
of other quinonoid mixtures to predators (references in Eisner, 1970, 
1972; Eisner and Meinwald 1966), there can be no doubt that the 
glands of Adelium are protective in function. The presence of the 
alkene may be of more than incidental significance. It has been 
argued (Blum and Crain, 1961), and in one case proven (Eisner 
et al 1961), that lipoidal additives promote spreading and penetra- 
tion of defensive secretions on target. 
Defensive glands of arthropods vary greatly in structure and oper- 
ation, and several characteristic types have been recognized (Eisner, 
1970). The glands of Adelium appear to combine features of two 
of these types. Basically, by virtue of their extrusibility, they clasify 
as conventional eversible glands, but since they occasionally eject their 
Table 1. Adelium pustulosum: Temporal characteristics of the chirps 
and morphological features of the stridulatory ridges. Temporal measure- 
ments were made from oscillograms and are given as mean ± standard 
error; sample size (N) is given in parenthesis. Morphological measure- 
ments were made from microscopic preparations of the last abdominal 
tergite of the beetles ; tooth spacing was calculated by dividing ridge length 
by tooth number. (The tergite of $ no. 1 was damaged in preparation, 
hence the omission of measurements from one ridge.) 
