THE CANADIAN ENTOMOLOGIST. 49 



• 



lasted for from thirty to forty seconds. Copulation did not follow in all 

 cases ; in several cases it did. The exciting process appears to be always 

 preliminary to copulation. 



The gland-like organ is found on the fourth antennal joint of the 

 male in Tropidopria and many allied genera, and it appears that its sole 

 purpose is for the exciting of the female in the manner described. 



Oviposition. — This takes place in the puparium. The earliest 

 instance was observed forty-eight hours after emergence. The ovipositor 

 is, in all cases, inserted directly back of the respiratory] "horns" in the 

 suture forming the cap, which is forced off by the Eristalis adult in 

 emerging. Freshly-found puparia were selected, when possible, for ovi- 

 position in preference to those in which the host was well advanced. It 

 was observed, however, that they would deposit their eggs in old puparia 

 when only one is exposed. Several such cases, even when the female was 

 known to be fertilized, did not harm the host, the adult Eristalis emerging. 

 The ovipositor appears to be inserted by a straight slow thrust ; the body 

 of the female while ovipositing is raised in a semi-circle, except for an 

 occasional movement of the antennae, which for the most part are extended 

 forward and rest upon the puparium. The time from the insertion to the 

 withdrawal of the ovipositor was taken in four cases, being 173 minutes, 

 185 minutes, 96 minutes and loi minutes respectively. 



Development. — The larva is an internal feeder, developing and trans- 

 forming within the soft tissues of the abdomen and thorax. In the early 

 stages they do not retard the development of the host, as in instances 

 where the puparia were known to be freshly formed when the eggs of the 

 parasites were deposited in them, and when one of these was broken open 

 fifteen days later the head, thorax and legs of the fly were found to be 

 perfectly formed. 



Length of cycle. — The two broods carried through from the egg to the 

 adult took, in one case, 36 days, from August 7th to September 12th, and 

 in the others 41 days, from September 7th to October i8th ; in this last 

 case the larval and egg stages were 30 days and the pupal 1 1 days. On 

 account of the difficulty found in rearing the larvae the cycle of the host 

 could not be determined accurately. Data taken in the latter half of 

 August and in September, when put together give the complete cycle at 

 about 30 days — about 18 days larvae and 12 days pupae — in all a shorter 

 cycle than that of the parasite. 



