i6o 
Psyche 
[September 
(b). Enhance the general resemblance of the insect to a stick by 
increasing the apparent length of the body and providing it with a 
long tapering termination, thereby adding to the plant-part mimicry 
and signalling false information about edibility to (insectivorous) 
predators. Experiments that show that some predators can use the 
presence of heads and legs as prey-detection cues are described by 
Robinson (1973). 
It seems probable that the behavioral and structural devices that 
serve to conceal prey-detection cues and also have a mimetic function 
evolved in the first place as part of a strategy of concealment and 
then constituted important steps towards the specializations involved 
in stick- or leaf-mimicry. Thus, for instance, insects that rest against 
a substrate can achieve maximum concealment by suppressing ‘relief’ 
or profile. This can be achieved by flattening or elongation, or both. 
Flattening could be a starting point for leaf-mimicry and elongation 
a starting point for stick-mimicry (examples in Robinson 1969b, but 
see also the recent careful study of Ghanian praying mantids by 
Edmunds 1972). Two examples of cryptic postures in tettigoniids 
from New Guinea are detailed in this paper. Both involve adapta- 
tions that are clearly related to concealment and at the same time 
dead-ends in the sense that they do not lie on the path to leaf-mimi- 
cry as it has been achieved in the orthoptera. Both adaptations are 
complex and interesting in themselves. Both involve the concealment 
of cue-structures and both involve profile reduction. 
Materials and Methods 
The insects were observed at the Wau Ecology Institute, Wau, 
Morobe District, New Guinea during the period April 1970 to 
April 1971, as part of a comprehensive study of insect anti-predator 
adaptations. This mainly involved the rich phasmid fauna of the 
area. 1 Both species were collected at night at the Institute and also 
at other localities in the Wau region. They were identified by Mrs. 
Judith Marshall of the British Museum (N.H.) London to whom 
the author is most grateful. Specimens are deposited with the Mu- 
seum. Behavioral observations were carried out both in the field 
and in a large screened insectary. More than ten specimens of each 
species were examined. 
Observations made on more than thirty species of phasmid will be pub- 
lished as soon as the insects can be identified. 
