196 
Psyche 
[September 
tenbacher (1908) from a single adult male and an immature female. 
The first adult female was described in 1957 by Rehn (loc cit). 
P. spinulosus is quite strongly sexually dimorphic. Adult males 
(Figures 1 and 2) are relatively thin and have well developed wings, 
whereas adult females (Figure 3) are much more robust, longer, 
and have reduced wings. Both sexes vary somewhat in ground color 
from light grey-brown to dead-leaf brown. In individual females 
the ground color may be interrupted by areas of pale lichenose colora- 
tion. The tegmina and the dorsal surface of the costal areas of the 
wings are concolorous with the body surface. 
Materials and Methods 
Two male and three female adult P. spinulosus were collected in 
the laboratory clearing on Barro Colorado Island, Canal Zone, 
Panama during July and August 1967. A further two females were 
collected in February 1968 and these proved to be last instar nymphs 
which successfully metamorphosed into adults whilst in captivity. 
All the insects were successfully maintained in culture on a diet of 
guava (Psidium sp.) leaves, provided on short stems which were re- 
newed twice weekly. Screen cages of one cubic meter proved satis- 
factory for the maintenance of these insects. The 1967 insects lived 
for over four months in these conditions; during this time mating 
was observed twice and a large number of eggs were laid. At the 
time of writing (April 1968) the 1968 individuals are still flourish- 
ing and nymphs from the 1967 eggs have reached the fourth instar. 
Details of the various elements of defensive behavior were ob- 
served both in the laboratory and under more natural conditions 
when the insects were placed in appropriate vegetation out of doors. 
The resting attitude and displays were photographed and filmed and 
the accompanying illustrations are based on 35mm color trans- 
parencies or single frames of 16mm movie film. The stridulation of 
the adult female was recorded on tape by my colleague Dr. A. S. 
Rand and the accompanying sonograms were produced from this 
recording through the cooperation of Dr. W. John Smith of the 
University of Pennsylvania. 
Elements of Defensive Behavior 
CONCEALMENT. 
The contribution of behavior to the concealment of stick and leaf 
mimicking insects is usually two-fold. The animal may adopt special 
attitudes when at rest or in response to stimuli which could signal 
