192 
Psyche 
[Vol. 88 
the tropics over a typical diurnal cycle. Different species may 
possess different levels of physiological capacity to cope with 
stressful environmental conditions imposed by either too much 
wetness or too little wetness. From my work on cicadas in Costa 
Rica over the past eleven years, and particularly from data on 
densities of nymphal skins of co-occurring species in the same 
patches of habitat, it seems doubtful that seasonal emergence 
patterns in cicadas is related to interspecific competition in develop- 
ing cicadas. From what little information I have, there is little 
reason to suspect competition for oviposition sites. But the great 
diversity in the properties of the calling songs among co-occurring 
species in tropical forests, and the tendency for several species to 
form single species aggregates of chorusing males (Young 1980c) 
suggest that there might be competition for optimal calling condi- 
tions. In cicadas, the calling song is a major component of fitness 
since it presumably functions in mating, and there might be strong 
selection to evolve allochronic emergence patterns when the calling 
songs of species conflict and reduce mating success. Certain types of 
seasonal changes in the environment, yet to be determined, may 
provide the most ready cues for these insects to exploit in evolving 
allochronic emergence patterns to reduce losses in mating success. 
The whole system warrants considerable detailed study as it involves 
different stages in the life cycle. Seasonal emergence may or may not 
have anything to do with conditions being intrinsically optimal for a 
certain species in a certain region at a certain time of the year. If the 
latter, the cicada is merely locking in to a convenient cue since, 
under this hypothesis, both wet and dry periods provide suitable 
resources for adults, including those associated with mating needs. 
Under the mating conflict hypothesis, it is implied that cicadas 
with very low densities and with unusual calling habits may forego 
entering into such a selection arena, thereby circumventing this 
adaptive pathway and emerging throughout most of the year, other 
things being equal. A typical case in point is the almost catholic 
habit of F. mannifera to sing for a brief period at dusk and under 
conditions of low population densities in Costa Rica (Young 1972; 
1980b; 1981b; this paper). The intensity of the presumed mating 
conflict is considered to increase as population densities of co- 
occurring species increase individually. 
In virtually all other regions studied, the greatest numbers of 
cicada nymphal skins occur beneath adult legume trees (Young 
