HABITS OF TWO TARASITES OF BLOW-Fl,IES. 221 



little chance of completing their development, and would probably 

 be killed by mites or some other enemy. 



Many attempts were made to obsei-ve the initial process of 

 making the exit-hole, but without success. However, on one 

 occasion a female was observed enlarging an exit-hole. A few 

 days previously this pnrticular puparium had been enclosed in a 

 glass tube stopped with a cork. The tube was under observation 

 with the aid of table binoculars to watch the movements of some 

 adults of both sexes which had emerged. There were two exit- 

 holes in the puparium, dorsally, with centres about 3 mm. apart, 

 one being much larger than the other, and through the former 

 all the hirge females in the tube must necessai'ily have escaped. 

 Suddenly a female's antennae were noticed to issue from the small 

 exit-hole, and wei'e violently ngitated. The upper part of the 

 epicranium could be seen against the inside of the puparium ; the 

 head was then moved, ;is was evident by the changing positions 

 of the waving antennae ; eventually, after the scnpes had several 

 times come into contact with the serrated edges of the exit-hole, 

 they were withdrawn ; the female could then be seen changing 

 its position. This accomplished, the head began to appear latero- 

 ventrally through the hole, the right eye coming up first ; 

 gradually more and more of the head appeared still maintaining 

 its latero-ventral aspect, until the edge of puparium was slightly 

 oblique to the junction of the mandibles. The right eye and 

 gena were then above the surface of the puparium, the antennte 

 still inside. The female now begnn to bite the puparium, the 

 right mandible coming down on it from the outside, the left 

 working up on it from inside. This process continued in a leaf- 

 eating-caterpillar-like movement- — semicircuhir forwards and 

 backwjirds — until the hole was made large enough to enable the 

 female to escape. No effort was made to test the size of the 

 hole; the insect continued to bite until, suddenly ceasing, it 

 began changing its position again until it was vential side up 

 inside the puparium, then, moving forward and bending upwai'ds, 

 the antennae, head, anterior legs, thorax, middle and posterior 

 legs, and abdomen appenred successively, until the female was on 

 the surface of the puparium, erect. It immediately began clean- 

 ing itself : the apex of the abdomen bore a. portion of the pupal 

 exuvia, which came away with a minute white meconial discharge. 

 A few seconds later the female was found by a male. 



In the laboi'atory, when the puparia are unbnried in soil, these 

 discharges can be seen scattered all over them, and ajipear as 

 minute white sti-ings. 



The Sexes. — Size : — The females a ary from TO mm. to 2-30 mm.^ 

 the males from 0'60 mm. to 2-0 mm. (6). 



General appearance. — Both sexes are distinguishable to the 

 naked ej'e. The females have large wings extending beyond the 

 apex of the abdomen, whereas the males (text-fig. 17) are semi- 

 apterous ; their rudimentar}'^ wings do not extend farther than 

 the third abdominal seg-ment. 



