HABITS OF T^YO PARASITES OF BLOW-FLIES. :-'41 



another Bracoiiid puparium was found with a dead adult half-way 

 out of it, the remainder were intact ; one of these was opened 

 and found to contain a living Braconid larva. The Chalcid- 

 infested puparia were all intact ; one was opened and contained 

 living larva^. The GalUpliora puparia were intact, and as the 

 outline of advanced fly-pupa could be seen in each, they were left 

 so ; the Galliiiliora larvse were all dead. The contents, except 

 the latter, were returned to the jar in their respective tubes, and 

 it was placed about 3 feet from a Bnnsen burner. On 16th 

 January one female Calliphora emerged, and in the next four 

 days all had emerged. The Chalcids commenced emerging on 

 30th Januaiy, and continued to do so for some days. The balance 

 of the Braconids began to emerge on 12th February. 



To summarize : both parasites were able to stand tlie test Avhen 

 put into the I'efrigerator in their respective full-grown larval 

 stage — that is, the customary hibernating condition. 



Conclusions upon the Economic Importance op 



AlYSJA MANBUCAJOK PaNZ. and NaSONIA BREVICOI^KIS ASHM. 



It is obvious that, in discussing this subject, the writer is only 

 able to treat of it from a theoretical standpoint. But in doing 

 so he is influenced by a desire to place on record some opinions 

 wliich have been formed during the course of this work, and some 

 of which gain cor.siderable support from the observations and 

 writings of those Avho have dealt with these parasites befoi'e him. 



It would appear that both parasites working in conjunction 

 would form an excellent combination, the one attacking the 

 larval stage, the other the pupal. And between them — it may 

 be assumed — a beneficial influence would be exerted in the control 

 of the Blow-fly. 



The occasional and accidental super-parasitism on the pait of 

 N. brevico^-ids is but an assurance of the maintenance of the 

 "Wave Law"*. It is actually a twofold assurance, because 

 although Nasonia may kill the Braconid, it may itself die in the 

 course of development or become entrapped — upon reaching the 

 imaginal stage — within the silk-lined puparium of the blow-fly 

 larva. 



Individually, Alysia manducatoi' is considerably superior to 

 Nasonia hrevicornis as an enemj" of the Blow-fl} . The former is 

 vastly superior in flight— in both sexes — a most important factor 

 where artificial distribution is concei'ned ; and it is also so from 

 the greater number of hosts it can injure and eliminate in the 

 course of breeding; the ratio is approximately 40 : 1. Its egg- 

 capacity is nearly four times greater than the Chalcid, and equal 

 to and in some cases greater than that of several species of blow- 

 flies. In length of imaginal life it is about equal to the Chalcid ; 

 the period of development from Qgg to imago is longei', and in 

 individuals of the same parent a considerable variation takes 



* Pointed out to the writer hj Prof, Lefroy. 



