Psyche 
[June 
”4 
19351 Stecher et al., i960). For a small, appropriately sensitive pre- 
dator, swallowing Apheloria may well have its deleterious aftereffects. 
However, predators do not usually consume Apheloria , but are 
repelled by the secretion and its vapors. Under such circumstances, 
exposure to hydrogen cyanide and systemic incorporation of the poison 
are likely to be minimal. It is by no means clear how hydrogen 
cyanide, as a dilute vapor, effects its repellent action. The possibility 
that it acts in conjunction (synergistic ?) with the aldehyde should 
not be dismissed. 
The cyanogenetic capacity of a millipede can be expressed in terms 
of the amount of cyanohydrin stored. A medium-sized Apheloria 
(1 g) with a near maximum generating capacity of 600 fig hydrogen 
cyanide, has an effective defensive payload of 3.0 mg mandelonitrile, 
or about 0.3% of body weight. Distributed equally among the ani- 
mal’s 22 glands, this amounts to an individual glandular load of 
O.13 mg ( ca . O.12 fil) or about 12% of the estimated volume ( 1 yttl) 
of the reservoir of a gland. Given its emulsified state, mandelonitrile 
could be expected to occupy only a fraction of the total volume of 
the reservoir. 
Attempts were made with Apheloria to determine the rate at which 
the contents of their glands are restored. Fifteen millipedes, reassayed 
within 8 days or less after initial depletion of their secretion, produced 
less than 15 fig hydrogen cyanide each. Another group of six, reas- 
sayed after 2 months, still had relatively low yield of 20 to 100 fig . 
Secretion is thus seen to be synthesized at a slow and somewhat vari- 
able rate. 5 Millipedes reassayed after four and five months produced 
little more than those reassayed after two months. However, this may 
reflect the fact that after two months the health of laboratory animals 
declined (as reflected by a sharp rise in mortality) and that their 
rate of secretory synthesis had become subnormal. Pseudopoly desmus 
apparently also reloads its glands slowly. When individuals that had 
been previously stimulated to depletion were subjected to rough han- 
dling several days later, they failed to give off the noticeable odor 
that is indicative of a discharge. 
In view of the slow rate of synthesis of secretion, it is clear that 
in the four days or less that elapsed between capture and first assay 
the individual millipedes could not have added substantially to their 
secretory resources. The variability in output depicted in Plate 16 is 
therefore probably a fair representation of the actual variability that 
5 No correlation was apparent between the magnitude of the initial yield 
and that subsequently obtained on reassay (a high initial output was 
sometimes followed by a relatively slow rate of synthesis, and vice versa). 
