PSYCHE 
Vol. 69 June, 1962 No. 2 
DEFENSE MECHANISMS OF ARTHROPODS. X. 
A PHEROMONE PROMOTING AGGREGATION 
IN AN APOSEMATIC DISTASTEFUL INSECT. 1 
By T. Eisner and F. C. Kafatos 2 
Department of Entomology, Cornell University, Ithaca, N. Y. 
A striking feature of many aposematic insects is their habit of main- 
taining dense and often conspicuous aggregations (Cott, 1957). Rather 
than spacing themselves more or less evenly throughout what is seem- 
ingly a uniformly favorable habitat, they occur in distinct, sporadically 
distributed clusters. Many meloid and coccinellid beetles, as well as 
J a variety of pentatomid, coreid, and lygaeid Hemiptera, among others, 
are well known for this habit. These insects possess chemical defense 
mechanisms that protect them against predators, and their tendency 
to advertise themselves to visually oriented predators such as birds by 
pooling their aposematic resources in a collective display, appears to 
have obvious adaptive value. Moreover, by restricting themselves to 
a few relatively widely-spaced sites, the insects are exposed to but a 
fraction of the total number of predators in the area. This is likely 
to be of particular importance with respect to predators such as birds, 
which are known in many cases to have well-delimited foraging terri- 
tories, and each of which may be expected to inflict a toll upon the 
insect population during the training period when the bird is learning 
to discriminate against the insect. Clearly, the fewer the foraging 
territories occupied, the greater will be the number of insects spared. 
Hitherto no studies have been made on the mechanism by which 
such aggregations are established and maintained. The purpose of 
This study was supported by Grant E-2908 of the U. S. Public Health 
Service. The work was done at the Southwestern Research Station of the 
American Museum of Natural History, Portal, Arizona. We are indebted to 
the director of the Station, Dr. Mont A. Cazier, for his generosity with equip- 
ment and facilities, and to Miss Abby Rockefeller, who assisted ably in this 
and related studies. 
2 New address: Biological Laboratories, Harvard University, Cambridge, 
Mass. 
Manuscript received by the editor January 9, 1962. 
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