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Psyche 
[March 
beetles four months later into carbon disulfide rather than methylene 
chloride failed to show this component, it is apparent that the diha- 
lide is an artifact derived from the olefin. 
Structure and Defensive Operation of the Glands 
Although the two beetles differ slightly in size and appearance — 
A. percatum is less rotund and longer (i. 5-1.9 cm) than A. pustu- 
losum ( 1 .3-1.5 cm) — their glandular apparatuses are essentially 
identical. No dissections of fresh beetles were made, but judging 
from what could be discerned from specimens somewhat inadequately 
preserved in ethanol, the glands are anatomically similar in both 
species and probably homologous to eversible glands such as have been 
described for other tenebrionids (Lengerken, 1925; Roth, 1945; 
Tschinkel, 1972). Such glands are basically cuticular sacs, ordinarily 
withheld in inverted condition within the body cavity, and presumably 
everted by blood pressure. What is unusual about the Adelium glands 
is that they extrude to such great lengths. For example, gland length 
in a specimen of A. percatum 1.8 cm long that was freeze-dried with 
its glands everted, was recorded at 0.8 cm. Relative to body size, the 
glands of these beetles must rate among the largest eversible glands 
known for insects. 
Examination of a glandular sac of A. percatum , treated with warm 
aqueous potassium hydroxide to remove all soft cellular parts, re- 
vealed a conventional membranous cuticular lining, with typical 
cuticular organelles attached (Fig. 8). Such organelles are a diag- 
nostic feature of many insect gland cells (references in Eisner, 1970), 
and the ones of Adelium resemble closely those described from cell 
type 1 in the defensive gland of the tenebrionid Eleodes longicollis 
(Eisner et al.> 1964). The organelles were distributed along the full 
length of the glandular sac, indicating that the secretory tissue is not 
restricted to a limited portion of the gland. 
Gentle handling of Adelium usually induced no gland eversion at 
all. Only when the animals were more forcibly stimulated, as when 
they were grasped by the body or an appendage and squeezed, did 
Figure 2. Pasture land near Gudgenby, A. C. T., Australia, where both 
species of Adelium were taken. Figs. 3-4. Adelium percatum responding 
to pinching of individual hindlegs by everting the gland of the side stimu- 
lated. Figs. 5-6. A. percatum responding to pinching of left midlegs. In 
Fig. 5 the gland has been maximally everted and has come into contact 
with the leg stimulated. In Fig. 6 the gland, on eversion, discharged part 
of its content as an anteriorly-directed spray (reference bar = 5mm). 
