462 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
c¢) 1 2 3 4 5 6 7 8 9 
Age (days) 
Ficure 3.—The relation between the regression coefficients of rocking response strength on 
flight time and age from eclosion. (See also fig. 1.) 
spans have a necessary upper limit which is determined by their food 
reserves at hatching. The relaxation of the brake on flight behavior 
must result in an immediately ensuing consumption of metabolic 
reserves, which will prove fatal. An upper limit to the hemileucine 
lifespan, then, is set by a physiological “clock” located in the central 
nervous system, and it is reasonable to examine the possibility that 
selection has acted upon the characteristics of this clock to modulate 
the longevities of different species. 
So far the available information is in excellent accord with this 
general hypothesis. For Automeris aurantiaca the calculated upper 
limit is about 9 to 10 days at 20° C., which is in good agreement with 
the order of the lifespan cbserved at this temperature. Although in 
virgin females flight behavior is blocked by inhibition from competing 
reproductive responses, namely, the assumption of the specialized 
calling posture in which receptive females await the arrival of mates, 
the death of males is preceded by just that burst of violent and un- 
