276 Trans. Acad. Sci. of St. Louis. 



It was not always possible to devote as many experi- 

 ments as desired to some particular problem, because the 

 supply or the characteristics of the material then at 

 hand would not permit. 



The insects usually left the cocoon during the after- 

 noon; this made exact records of emergence possible. 

 The sexes for this year were about equal in number, and 

 their habits monogamous.^ 



The mating cages were ordinary dome-shaped wire 

 dish-covers measuring 32 inches in circumference. Each 

 cage contained from two to four individuals, some of 

 which were marked with ordinary writing fluid. 



After the first fifteen experiments, the work became 

 too complex, and details on behavior could not be re- 

 corded. The notes are given essentially as they were 

 jotted down as each experiment was in progress; the 

 conclusions and comparative notes were added later. 



The insects were all normal and unmated unless other- 

 wise stated. 



It gives me pleasure to here acknowledge my indebt- 

 edness to my wife for valuable co-operation in tlie prep- 

 aration of the manuscript. 



Experiments. 

 Experiment 1. — April 21, 5:00 P. M. 



9 1. Age 7 days 20:30 hours. 

 $ 2. Age 6 days 3:30 hours. 

 c^3. Age days 1:30 hours. 



Object. — Will the male select tlie older or the younger 

 female ? 



Behavior. — 5:00. The females immediately become active when the 

 male is placed with them; he shows no eagerness to mate. — 5:20. The 

 male is now also actively fluttering about. The ovipositor of female 1 

 has been completely protruded, and in so doing, an egg dropped. — 

 5:21. The male and female 2 have become calm, but female 1 con- 

 tinues to vibrate the wings nervously at the farthest side of the cage. 

 She makes her way to the male, chasing him as it were for a short 



*See page 310. 



