456 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
themselves stimulate small birds to attack, it is reasonable to suppose 
that selection should act to eliminate these movements, and such has 
been the case. 
The next stage in the evolutionary succession is a simple one: the 
elimination of the rhythmic components, which has been achieved 
merely by raising their threshold. Some species, for example, A. 
memusae, perform the rhythmic part of their display to very light 
tactile stimulation; others (e.g., A. coresus) require strong tactile 
stimulation before it can be elicited, even to the point of mutilation. 
Further species, such as A. tridens, appear to be behaviorally poly- 
morphic. Some individuals of a population can be made to “hop” 
if violently treated, others cannot, and the differences are individually 
consistent over periods of days; finally, some species (e.g., A. godarti) 
never perform a rhythmic display. 
Meanwhile, certain other changes have been taking place. Whereas 
no species of Automeris is highly unpalatable, there are at least dif- 
ferences in their degree of acceptability to predators. A. fouchert 
is eaten readily by coatis and by the relatively unfastidious mar- 
mosets. A. junonia is accepted by marmosets but rejected by coatis. 
Whether this trend toward unpalatability is another aspect of the 
changes in the display pattern is not yet certainly known, but it 
seems likely. Certainly, an increasing feature of the more specialized 
displays is the introduction of curling components of the abdomen. 
In the species with full eyespot displays, this component merely 
tends to increase the apparent size of the displaying moth. But, 
ultimately, it becomes linked with another evolutionary trend, the 
reduction and, eventually, the elimination of the eyespot patterns 
themselves. Now in some species, such as Automeris aurantiaca, the 
eyespots have become reduced; the abdomen, on the other hand, is 
more strongly curled during display, and especially so in females, 
whose abdomens are so swollen with eggs that, curled, they present a 
series of greenish-white bars (the egg mass shining through the inter- 
seemental membrane). The hindwings are also protracted so that 
the abdomen is made visible from above. There is also a tendency 
for both pairs of wings to be somewhat elevated. In more highly 
evolved species (e.g., Automerina auletes, Hyperchiria nausica) the 
abdominal curling is yet more marked, and the wings are even more 
strongly elevated, now exposing the lateral aspects of the abdomen 
while not wholly concealing the small eyespots. 
This little series has been followed out in a very restricted group 
of closely related genera. The next stages are not found in this 
group, but appear to follow from it so logically that there is no 
doubt of their starting point. The genus Hylesia contains a large 
number of small brownish moths, clearly derived from the Automeris 
group of genera, probably from Gamelia (Michener, 1952). Most, 
