1962] 
Eisner and Kafatos — Defense Mechanisms 
59 
using porous nets of white cloth to enclose the groups of lycids, dis- 
tributed as before on close clusters of Melilotus branches (Plate 4, 
fig. 1 ) . The technique had the added advantage of preventing dispersal 
of the decoy group, while at the same time facilitating the count of 
newcomers assembled around the nets. Four nets were staked out with 
150 lycids each, two of them containing only males, the other two only 
females. Spacing was maximized within the area available, each net 
being about 25 m. from its neighbors. The loci selected were known to 
have supported no previous aggregations. Table II summarizes the 
results. Only those lycids were counted as newcomers which were 
either directly upon the nets, or on Melilotus branches within a few 
feet around them. It is clear that the males, but not the females, 
exerted immediate and persistent attraction for lycids of both sexes. 
The fact that the newcomers included a preponderance of males 
should not be taken to reflect a greater susceptibility of this sex to 
the attracting stimulus, since the males were actually the more 
numerous in the population at the time (actual counts made, based 
on samplings from the main population site, showed the ratio to vary 
between 3 : 1 and 6:1). 
The possibility was ruled out that ecological factors, rather than 
the males themselves, were the source of attraction. After the third 
day, the males from net A were exchanged with the females fromi net 
D. The other two nets were dismantled, and the lycids within them, 
plus the assemblages that had accumulated around both original male 
sites, were scattered at 1 m. intervals throughout the test area. Over 
the next three days only one assemblage built up, this time around the 
new male site (Table II). Clearly, the attracting stimulus is emitted 
by the males, and it is most likely a diffusible chemical factor. 
An additional observation is worth mentioning. On two separate 
occasions, when artificially induced aggregations were allowed to 
persist over a period of several days, and were subsequently removed, 
the Melilotus branches that had harbored the beetles were found to 
retain the potential to lure lycids, presumably as a result of residual 
attractant with which the plants had been labelled. When the lycids 
that would subsequently accumulate on these branches were sytemati- 
cally removed once a day, and redispersed, the attractiveness, of the 
plants dwindled to extinction within a few days. 
The attraction of lycids to each other in the presence of males was 
also demonstrated in captive specimens. Mixed lots of males and 
females confined in glass-topped observation enclosures would soon 
distribute themselves into individual mating pairs or small clusters of 
