6o 
Psyche 
[June 
pairs. Females alone remained distributed singly and showed no 
attraction for each other. Males, by contrast, clustered closely, usually 
one on top of the other in overlapping sequence, as shown in Plate 4, 
fig. 2. 
A chemical attractant of the type involved here may appropriately 
be called a pheromone. Pheromones, by definition (Karlson and 
Butenandt, 1959), are substances secreted by one individual to the 
outside, capable of eliciting specific behavioral or developmental 
responses in another individual of the same species. Among insects, 
these social chemical messengers include the sex attractants, the queen 
substance of honeybees, the trail substances of ants and termites, the 
releasers of alarm behavior in ants, etc. It is clear that the lycid attrac- 
tant, aside from its obvious function in maintaining the aposematic 
population densely congregated, also serves appropriately in bringing 
together the sexes preparatory to mating. But since it lures both 
males and females with apparently equal effectiveness, there must be 
additional short-range stimuli operating within the aggregation to 
insure that males and females will ultimately be properly paired. One 
wonders what evolutionary justification accounts for the production 
of attractant by the males alone, rather than by the females, or by 
both sexes. Not enough is known about the life cycle of lycids, but the 
possibility that the males are the first to emerge in the season and 
hence are the ones that carry the aggregations through their incipiency, 
is worth considering. 
It is hoped, now that the groundwork of this problem has been laid, 
that additional more precise experimentation on this unusual type of 
attractant will be pursued. With L. loripes there are some especially 
intriguing aspects to the problem. This lycid is the dominant Mulleri- 
an element of an elaborate mimetic complex (Linsley et al., 1961) 
that includes among others, a congeneric sibling species of lycid \Lycus 
simulans (Schaeffer)], a cerambycid beetle ( Elytroleptus ignitus 
LeConte), and a geometrid moth [ Eubaphe unicolor (Robinson)]. 
Whether the attractant produced by L. loripes , which far outnumbers 
the others, exerts its action also on all or some of the mimetic associates, 
thus insuring that these are lured to “safety” within the aggregations 
of the dominant model element, remains unknown. Unfortunately all 
of these mimetic forms were extremely scarce at the time of our experi- 
ments, and could not be included for study. 
Future work should concentrate also on some of the many other 
gregarious aposematic insects known, in which similar attractant 
mechanisms, or perhaps interesting alternatives, are likely to be at play. 
