io8 
Psyche 
[June 
Text-fig. 1. Apheloria corrugata (above) and Pseudopolydesmus ser- 
ratus. 
in such a way that the contents of the two compartments are mixed, 
and cyanogenesis is initiated, at the instant of discharge. Cyanide 
liberation proceeds gradually, and persists for minutes after the dis- 
charge (H. E. Eisner et ah, 1963; T. Eisner et ah, 1963). The 
secretion and its vapors are strongly repellent to predators (T. Eisner 
and H. E. Eisner, 1965). Apheloria may discharge from one, several, 
or all glands, depending on the severity of the attack. A single ant, 
biting one of the millipede’s legs, may cause only the gland nearest 
that leg to discharge, but this suffices to deter the assailant. A larger 
predator, or a swarm of ants, may inflict more generalized trauma 
and cause a number of glands to discharge. Ejection from all glands 
occurs only in response to unrestricted disturbance, such as rough 
handling. The preceding probably applies also to Pseudopoly desmus } 
which is known to generate hydrogen cyanide (H. E. Eisner et al., 
1963), and which we have found to possess two-compartmented 
glands essentially similar to those of A pheloria. However, it is not 
known whether Pseudopolydesmus also generates hydrogen cyanide 
by dissociation of mandelonitrile. The fact that its secretion has an 
odor distinctly different from that of benzaldehyde suggests that it 
may store a cyanohydrin other than mandelonitrile or, alternatively, 
that its secretion contains additional compounds capable of masking 
the odor of benzaldehyde. 
