Rau — Sexual Selection Experiments in Cecwpia Moth. 285 



male it is easy to see that the larger female 54 is the more attractive 

 to him. The smaller female seems to exert every effort to attract his 

 attention. — 7:43. Judging from previous experiments we would expect 

 all three insects to remain perfectly quiet until mating takes place, 

 but now we see female 57 giving an occasional, abrupt, hard blow with 

 her wings against the wing of the male, causing him each time to 

 respond in a similar manner. — 7:45. We see this female slyly moving 

 so close to the male as to gently touch the ventral portion of his 

 abdomen with her wings as they hang. The male each time puts out 

 one of his fore-legs and touches the wing as it comes toward him, but 

 whether to resist this caressing or to encourage it cannot be deter- 

 mined. — 8:00. This behavior has continued up to the present, and 

 now all are at rest, the two females at about equal distances from the 

 male. The ovipositor of female 54 is exposed. All the indications are 

 that the large moth will soon mate. — May 2, 8:00 A. M. The male is 

 now found in copulo with female 57, the smaller and less beautiful 

 insect. Was she chosen because she was about a day younger, or 

 because of her persistent obtrusiveness?* 



Experiment 11.— May 1, 8 :30 P. M. 



c?C2. Age days 4:40 hours. Very small; the two left wings 

 badly deformed; length of body, 2.8 cm.; width of 

 abdomen, 0.8 cm.; expanse of fore-wings, 11.5 cm. 



^11. Age 3 days 7 : 35 hours. Length of body, 3,8 cm. ; width 

 of body, 1.1 cm.; expanse of forewings, 15 cm. 



$ 56. Age 1 day 1:30 hours. 



Object, — ^^^ill a small, deformed, young male be pre- 

 ferred to a large, well-formed male 3 days older? 



Behavior. — 8:30. The female remains calmly clinging to the wires 

 when the males are admitted. After a few seconds' rest, male 17 flut- 

 ters against her, roughly knocking her to the floor. Again and again 

 she attempts to remount, but each time is beaten back. Sometimes she 

 is successful in reaching the top, but often she is thrown down before 

 reaching half way. Since the first few falls of the female, male 62 has 

 taken his position at the top of the cage. I wonder if this young male 

 may be the attraction which leads the female repeatedly to try to reach 

 the top. Perhaps this is also why male 17 continually hinders her 

 progress. Eight times the female has attempted to mount to the top, 

 and each time male 17 has fought her back. At last however she has 

 gained the dome and has quietly taken up her position about an inch 

 and a half from male 62. They both gently move their wings to and 

 fro. Their positions are such (suspended by the fore-legs) that every 

 time she closes her wings she entirely covers the wings and body of 



* Anyone observing a few unmated Cecropias together at night will 

 be at once convinced that this behavior is far from accidental. 



