162 MISCELLANEOUS PAPEES. 



Table XIII. — Oviparous {/eiicration of Sipha flava, 1906. 



The average time for the 21 cases in which an exact record was kept 

 was 19.5 days. The sexes were first observed in copuhi October 18, 

 and this was noted occasionally until December 3. At this latter date 

 the temperature in the room where the aphides were kept was 45° F. 

 In 1905 the earliest record of copulation was October 17, and the first 

 eggs were found soon after. As a rule the eggs were laid on the 

 underside of the sorghum leaf, but as might be expected there were 

 some exceptions to this; for example, eggs were sometimes laid on the 

 side of a cage and on the stem of a plant. November 21, 1907, at 

 Urbana, 111., I found oviparous females on grass, but eggs were not 

 found. This, with the fact that the earliest spring records of finding 

 them out of doors have been on grass, indicate that grass is the alter- 

 nate food plant to which the sexupara? migrate in the fall to produce 

 the sexual forms. The number of eggs laid by this species varied, acc- 

 cording to my observations, up to 11, and in 19 ca.ses the average was 

 8.3 eggs per female. There was no uniform period from the laying of 



