1968] 
Robinson — Behavior of Pterinoxylus 
197 
the presence of a predator and these may enhance the resemblance 
to the object mimicked. In addition, the animal may suppress move- 
ments which could attract the attention of predators either by being 
nocturnally active or by “freezing” in response to disturbance. P. 
spinulosus is active at night and assumes a resting attitude by day 
at all stages of development. Most stick mimicking phasmids pro- 
tract the anterior limbs, side by side, in line with the long axis, in 
a resting attitude which increases the apparent length of the body 
(See Chopard 1938 for a partial review of phasmid resting attitudes). 
Anterior limb protraction occurs in P. spinulosus but is accompanied 
by special attitudes of the intermediate and posterior legs. These are 
shown in Figure 1. As can be seen from inset A (figure 1), the 
tibiae and tarsi of the intermediate legs are closely apposed to the 
inferior surface of the femora. The apparent units so formed 
project at an angle above the dorsal surface of the thorax. Because 
of the close apposition of the tibia and tarsus to the femur, which 
has tabulated inferior margins, the separate elements of the folded 
and projecting leg are concealed. The posterior legs are held in an 
attitude which varies somewhat with the configuration of the sub- 
strate but project ventrally and often posteriorly (as shown in inset 
B, Figure 1.). The relatively short tibiae are apposed to the in- 
ferior surface of the femora and the tarsi are placed along or around 
the twig. 
Figure 1. The resting attitude of Pterinoxylus spinulosus Redtenbacher. 
Note the details of the attitudes of the intermediate and posterior legs 
as shown in insets A and B. (Based on a 35mm color transparency). 
