SYRPHIDAE OF MAINE. 



227 



on the bodies of Musca domestica and Chortophila pusilla; the larvje 

 attacked these flies at the junction of the neck with the thorax and held 

 on for one or two days before pupating." 



On July 24, 191 5, I found in a field of oats and wild mustard 

 on the Station farm, many females of this species, their abdo- 

 mens greatly distended with eggs. They seemed to be feeding 

 on the blossoms of the mustard and no signs of oviposition 

 were found. No aphids could be found on these plants. The 

 ova of the flies were plainly visible through the thin, distended 

 and transparent abdominal sterna and pleura, especially of the 

 posterior half of the abdomen. Only a single male was taken 

 and no others seen. Whether this indicates a relative scarcity 

 of males or simply that the gravid females were more easily 

 taken I am unable to say, — propably the former. 



Twelve females were placed in jars with the single (avail- 

 able) male. Two days later July 26, 7 A. M., a large number 

 of eggs had been deposited on the sides of the jar and on grass 

 enclosed ; probably having been laid during the night. July 

 28 by 8 A. M., the eggs were hatching, the duration in the 

 egg stage having been between two and two and a half days. 

 Not being certain of the larval habits, I placed the young in a 

 variety of situations and offered them a variety of substances 

 for food. The only noticeable result was the decided prefer- 

 ence shown by the larvae for very moist situations. From the 

 variety of aphids offered them they seemed to show a preference 

 for Aphis cornifoliae from Corniis although no larvae were 

 found among this species in the field. 



The larvae fed in captivity developed rapidly and began 

 pupating August 14. 



The following are the dates of pupation and subsequent 

 emergence of adults from the eggs laid July 26. 



Pupated August 14 Parasite emerged August 26 



16 



$ 



1 a 



26 



« l7 



9 



I U 



23 



" 20 



2 



I ce 



27 



" 20 



9 



t (t 



30 



u 23 



2 



Sept. 



3 



26 





< (i 



4 



Again on August 12 a female in captivity deposited a num- 

 ber of eggs. They were placed quite rapidly at intervals of 



