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[Vol. 88 
increases greatly over a period of years, even though the root crowns 
and other cicada-related characteristics of other trees are equally 
suitable for cicada development. 
Since all plots were located at or withn the lower one-fourth of 
the ravine, the instances in which some species, such as F. n.sp. and 
Carineta sp. call primarily from the top of the ravine and not at the 
bottom suggests a behavioral response associated with mating 
requirements. Such species presumably emerge near the bottom of 
the ravine and fly up to the top for courtship. Such species may also 
emerge near the top as well although this was not determined in this 
study. The observed patterns of adult calling sites within the ravine 
are presumably related to the acoustical and thermoregulatory 
needs of each species. 
Summary 
The genera and species of cicadas, their seasonal distributions, 
habits, and emergence sites were studied discontinuously over 
several years at the Cuesta Angel ravine, a rugged mountain tropical 
wet forest locality in the northern portion of the Central Cordillera 
of Costa Rica. Emphasis was placed on determining the distribution 
of cicadas down one steep forested side of this approximately 300- 
meter deep ravine and along a representative portion of its bottom 
(Rio Sarapiqui). Some evidence of seasonal fluctuations in abun 
dance was obtained for the six species found here, and the greatest 
densities of nymphal skins of all species were found in small plots 
around individual legume trees. Densities in the large river-edge 
plots, containing many different kinds of trees, were relatively very 
low. The data are compared to similar data on cicadas from other 
regions of Costa Rica. Tropical cicada seasonality, interactions with 
Leguminosae, and possible mechanisms underlying population den- 
sities, are discussed. 
Acknowledgements 
This research was originally supported by National Science 
Foundation Grant BG-33060 of the United States of America, and 
subsequently by the Milwaukee Public Museum. Field assistance 
was given (1972-73) by students from Lawrence University. Dr. J. 
Robert Hunter, then Director, Costa Rican Field Studies Program 
of The Associated Colleges of the Midwest, provided logistical 
