28 o 
Psyche 
[September 
attracts females. Both contact chemoreception of this hypothetical 
substance and tactile stimulation resulting from contact with a 
male may be involved in the release of subsequent mounting behavior. 
This male sex pheromone must be produced by inactive males, as 
females approach and mount actively before males show any signs 
of sexual arousal. 
The most puzzling feature of the courtship of this species is the 
lateral vibration movement, which characteristically appears in males 
after a brief exposure to courting females. The stimuli involved in 
the release of this movement, its function, and its possible motiva- 
tional basis remain obscure. Observations indicate that this movement 
appears in a bewildering variety of situations within the general 
context of mating behavior. It occurs most frequently in isolated 
males upon exposure to virgin females which are actively engaged 
in mounting attempts. Under these circumstanceSj it may appear 
in males which are being mounted by females, in males which are 
being touched by the antennae of females, and occasionally in males 
which have no contact with another animal at all. In the latter 
case, the possible role of contact with a virgin female just previous 
to the observed display can not be discounted. Lateral vibration may 
be shown by a male which is mounting another vibrating male. It 
frequently appears in the male upon separation of a pair after an 
unsuccessful copulation attempt. It has also been observed in males 
which were attempting to escape from mounting females. Once or 
twice it has been observed in isolated males in the absence of 
females. This movement also occurs, though less commonly, in 
females, in which it is confined to two situations: a) in situations 
preceding mounting, in which the female has made antennal contact 
with the antennae of a vibrating male, and b) sometimes after un- 
successful copulation attempts. 
The nature of the stimuli involved in the release of lateral vibra- 
tion remains uncertain, but it seems unlikely that it is normally 
released by tactile stimulation alone, although the latter is evidently 
sufficient in a few instances as the display occasionally appears in 
isolated males. There is no satisfactory evidence that a volatile 
pheromone is involved, though the display is sometimes given by 
animals lacking contact with other animals. It was not possible to 
release this movement in isolated males by providing them with 
pieces of filter paper which had lined containers of virgin females 
for varying periods of time. Animals which accidentally wander 
onto such pieces of filter paper occasionally examine them with 
their antennae and palps (holding the maxillary palps against the 
