178 BUTTERFLIES 



so busily engaged that I was able to draw near and watch 

 the operation for some time before she flew away. As 

 soon as she was gone I was much interested to see a tiny 

 parasitic fly running eagerly over the newly laid eggs, and 

 this fly also was so busily interested in her work that I was 

 able to cut the twig off and sit down to observe at leisure 

 through a lens the actions of the insect. I dictated to a 

 companion my notes of these observations and so was 

 able to get rather a complete record of the process of ovi- 

 position. 



The tiny fly would stop over one of the butterfly eggs, 

 holding its body vertical with the hind legs far back 

 and the other legs so straightened out as to hold the front 

 of the body high up. Then it would insert its tiny ovi- 

 positor through the egg shell and proceed to deposit an 

 egg of its own inside of the larger egg of the butterfly. 

 At least it seemed a safe assumption that this was what 

 happened although of course it was impossible to see the 

 smaller egg at the time. While thus engaged the anten- 

 nae of the tiny fly were bent directly downward to the egg 

 beneath. In about a minute the fly withdrew its ovi- 

 positor and after running around for a few seconds again 

 settled upon another egg and repeated the operation. 

 Then it tried again on a third egg, after which I got out 

 my watch and began timing the process. These are the 

 results in the case of the next dozen eggs that were laid. 

 It required : 

 94 sec. to lay egg No. 4. Then fly moved around 26 sec. 



