1974] 
Eisner et al. — T'enebrionid Beetles 
201 
dominal tip (first syllable), and of both ridges with somewhat 
unequal force during the upward movement of the tip (second syl- 
lable) . This conclusion rests on the observation that the syllables 
contain, in addition to a consistent major pulse (which in total num- 
ber per syllable corresponds to the number of teeth per length of file 
estimated to be scraped during a syllable) 1 , a subsidiary pulse of 
varying lesser amplitude, which appears sporadically in the first syl- 
lable, and fairly consistently in the second syllable. These lesser 
pulses, when they appear, result in a doubling of the pulse repetition 
rate. Moreover they bear a shifting rather than fixed temporal rela- 
tionship to the primary pulses, suggesting that they are not subsidiary 
acoustical concomitants of single tooth scrapings, but a consequence 
of scraping of a second set of teeth of somewhat unmatched spacing 
relative to the first. The near absence of secondary pulses in the first 
syllable suggests that the beetle might not press the abdominal tip as 
vigorously against the elytral margins during downward abdominal 
deflection as during the return motion. 
Discussion 
Defensive glands that produce quinones are widespread among 
arthropods. They have been reported not only from other Tene- 
brionidae (references in Jacobson, 1966; Roth and Eisner, 1962; 
Weatherston, 1967; Weatherston and Percy, 1970), but also from 
certain termites (Moore, 1968), earwigs (Eisner and Blumberg, 
1959; Schildknecht and Weis, i960), cockroaches (Roth and Stay, 
1958), grasshoppers (Eisner et al., 1971a), carabid beetles (Anes- 
hansley et al., 1969; references in Moore and Wallbank, 1968; 
Schildknecht et al., 1968), staphylinid beetles (Blum et al., 1971; 
Brand et al., 1973), millipedes (references in Jacobson, 1966; Roth 
and Eisner, 1962; Weatherston, 1967; Weatherston and Percy, 
1970) and opilionids (Fieser and Ardao, 1956; Eisner et al., 1971b). 
As is often the case with arthropod defenses, they exist as close 
counterparts in plants: glandular hairs that secrete a benzoquinone 
have been described for Primula obconica (Schildknecht et al., 1967). 
Contrary to claim (Schildknecht et al., 1964), not all Tenebrionidae 
J From photographs such as Figs. 10 and 11, which depict the motion of 
the abdominal tip during chirping, it was estimated that this motion has a 
maximum amplitude of ca. 2/3 the length of a serrated ridge. This cor- 
responds to about 130 teeth, a figure in line with the counted maxima of 
major pulses in the syllables. 
