CHALCID PARASITES OF MUSOCID FLIES IN AUSTRALIA. 
that flies had emerged from only 15 per cent. of them. The remaining’ 
pup were placed in tubes. On 15th December, several small black ant- 
like chaleids, averaging about 8 mm. in length, were noticed, more emerg- 
ing during the succeeding days. As they appeared, the little insects were 
transferred to a large jar, the end of which was covered with a piece 
of cloth, and were fed by smearing honey and water on the cloth. 
Copulation was observed to occur at once, and females readily attacked 
fresh fly pupe on the day of emergence. 
When about to oviposit, the female walks over the pups, testing the 
surface with her long flexible antennew. <A suitable place having been 
found the sharp, piercing stylet connected with the ovipositor is 
brought into play, and a tiny hole bored in the chitin of the puparium. 
A few minutes is usually sufficient’ to effect a puncture, the stylet being 
thrust for its whole length into the wound. 
The eggs are minute oval structures, measuring from 0.4 to 0.45 mm. 
in length by 0.1 mm. in breadth. The shell is minutely papillose, except 
at one end, which is drawn out into a blunt projection varying some- 
what in length. This point is not obvious in the uterine egg. The larve, 
on hatching, is a tiny white segmented creature, which applies its mouth 
to the surface of the fly pupa, and gradually increases in size at the 
latter’s expense. When the chalcid larve pupates, it assumes the form 
of the adult, the structures being, however, soft and white, and sur- 
rounded ‘by a clear envelope. During the pupation stage, the hard 
chitinous cuticle of the imago is developed. . When the insect is ready to 
leave the pupa case of its host, it gnaws an irregular hole at the anterior 
end and crawls out. Nothing is left of the fly pupa by this time but a 
dark shrivelled mass. Both sexes of the chalcid are capable of flight 
immediately upon emergence. 
The sexes differ in the form of the abdomen, which is shorter and. 
more spindle-shaped in the male, whereas that of the female has a pro- 
minent projecting terminal region, and in the shape of the head, which 
in front view is seen to be relatively broader and shorter in the male. 
The antenne are also unlike. : 
As far as our experience goes, only one chalcid develops in each para- 
sitized fly pupa, thus from 53 pupa cases of which individual record 
was kept, only 53 chalcids emerged. The sizeof the perfect insect 
depends upon the size of the pupa in which it developed. Two Spalangia 
have occasionally been seen ovipositing at the same time in one pups. 
The period of time elapsing during summer (December and February) 
between the laying of the ege and the emergence of the wasp is between 
three and four weeks (21 to 28 days). 
Tt was found that in Texas, United States of America, during the 
colder weather, the period ranged from 61 to 109 days, while during 
winter the adult did not emerge, the insect apparently overwintering in 
its pupa stage. : 
Our results show that larval development is passed through very 
rapidly under Queensland summer conditions. This is a factor which 
renders it particularly valuable as a means of controlling the spread 
of noxious Muscids in this State. 
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