■c;halcid parasites of Australian sheep maggot-flies. 101 



and are frequently seen sitting on the breeding-jars, or walking 

 over the soil in search of pupae. When a suitable pupa is 

 found tlie wasp walks over it, testing the shell with its antennae, 

 and when a favourable spot has been found inserts its ovi- 

 positor (ftgs. 5, 6, 7), taking up the curious attitudes that 

 have been described by various workers. During the process 

 of piercing the pupal shell an oilj' fluid is seen running dowai 

 the ovipositor, evidently acting as a lubricant. During 

 oviposition, which lasts from a few minutes to a quarter of 

 an hour (or even 25 minutes, Froggatt and McCarthy ; 30 

 minutes, Altson), a number of eggs, generally about 15 to 

 ^0, but sometimes only one or two, are deposited on the surface 

 of the developing fly (fig. 29). On several occasions it was 

 observed that, although the ovipositor had been inserted for 

 quite a long time, no eggs were deposited. The ovipositor is a 

 moderately long structure, and, as it is inserted to its full 

 length, the wasp places the eggs in clusters, sometimes at a 

 -considerable distance from the punrture. 



Egg {fig. 27). — The egg is whitish and somewhat trans- 

 parent, measuring, Avhen freshly laid, about -32 mm. in length 

 by -08 to -12 mm. in breadth. It appears to contain a small 

 amount of yolk. During development Ihe egg frequently 

 lengthens a little. The duration of the egg period is exceedingly 

 important econcmicall}'^ (as will be described more lully below), 

 and, according to published observations, varies from 30 to 

 74 hours. The time in Brisbane in midsummer was found to 

 be 40 hours. 



Larva. — ^This, on hatching,' is a small whitish maggot 

 about -3 mm. long, which maintains the same general appear- 

 ance throughout larval life. The larvae do not appear to 

 move far from their original source of attachment, but can 

 be seen clustered together where the eggs were originally 

 placed (fig. 20). Here they appear to remain throughout the 

 feeding period, which is about 4?7 to 5 days (7 to 10 in London, 

 Altson). The three instars are easily recognisable by the 

 structure of the jaws, which in the first instar are long, slender, 

 slightly curved, stylet-like structures, serving to penetrate 

 the epidermis of the developing fly (fig. 30). The larva of the 

 second instar is much larger than that in the first stage (fig. 

 31) ; the jaws are more powerful, and the whole larva appears 

 much more heavily chitinised (fig. 32). The jaws of the larva 



