HABITS OF TWO PARASITES OF BLOW-FLIES. 



237 



sloping backwards ventrally, and wbicli is attached to a trapering 

 thorax, narrowest at the back of the head, and cei tainly better 

 adapted for burrowing in loose soil. 



The last point investigated was an examination of all the 

 puparia contained in two jars, of parasitized material obtained 

 in the open. The contents of these jars, it should be explained, 

 were the result of exposing meat on soil in a glass receptacle at 

 the Society's Gardens, wath the o])ject of obtaining additional 

 supplies of the Braconid. Tlie collection of the contents of this 

 receptacle was delayed until 14th August, and when sorting out 

 the intact puparia from those from which blow-flies had emei'ged, 

 the writer came across a few dead female Nasonia as well as dead 

 female A. mandiicator. It was therefore assumed that a double 

 infestation had taken })lace. At the time, an attempt was made 

 to differentiate between the puparium of one or other of the 

 parasites, but both were in too early a stage to disclose any 

 difference when subjected to transmitted light. The material 

 was consecjuently left unsorted, a,nd emptied into two jars to 

 await developments. Nasonia began to emei-ge on 31st August, 

 and in order to give these an opportunity of escaping as they 

 emerged, the linen covers of the jars were replaced by pieces of 

 mosquito netting, through the mesh of which the females were 

 able to escape. Both jars were placed inside a large glass cylinder. 

 This was used as the cage, and in it were put dishes with supplies 

 of blow-fly puparia for the Chalcids. On 3rd September 

 A. manducator began to emerge; the Chalcids were still doing so. 

 This continued until 29th September. This state of afi'fdrs neces- 

 sitated constant handling of the jars to release the Braconids, so 

 that the contents became disturbed ; and although it was not 

 observed at the time, it now transpires that some of the Nasonia 

 females never left the jars, but proceeded to super-parasitize the 

 Braconids in their puparia, and, further, some of those — the 

 progenitors of the above — found dead in the receptacle when 

 the material was collected probably did the same. 



When all the puparia had been collected from the jars, they 

 were sorted under three headings : — (A) Those from which 

 A. manducator had emerged, (B) those from which Nasonia had 

 emerged, and (C) those which were intact. Those from which 

 blowflies had emerged had already been removed, and the number 

 is not known. The numbers under the three headings were: — 

 (A) 195, (B) 50, (C) 506. Those under (A) were put a.side, those 

 under (B) were dissected for evidence of successful super-para- 

 sitism, and those under (C) were dissected and classified under 

 several headings as follows : — 



(1) Atrophied fly-nymphs 



(2) Dead fully-formed flies. 



(3) ,, Braconid larva?. 



(4) „ „ pupffi. I 



(5) ., „ adults, i 



(6) Active ,, larva?. J 



r-No signs of Chalcid attack. 



