yn 



CECIDOMYIIDAE 46 1 



others that this kind of paedogenesis occurs in several species of 

 the genera Miastor and Oligarccs. The details are briefly as 

 follows : — A female fly lays a few, very large, eggs, out of 

 each of which comes a larva, that does not go on to the 

 perfect state, but produces in its interior young larvae that, 

 after consuming the interior of the body of the parent larva, 

 escape by making a hole in the skin, and thereafter subsist 

 externally in a natural manner. This larval reproduction may 

 be continued for several generations, through autumn, winter, 

 and spring till the following summer, when a generation of the 

 larvae goes on to pupation and the mature, sexually perfect fly 

 appears. Much discussion has taken place as to the mode 

 of origination of the larvae ; Cams and others thought they 

 were produced from the rudimental, or immature ovaries of the 

 parent larva. Jleinert, who has made a special study of the 

 subject,-' finds, however, that this is not the case ; in the repro- 

 ducing larva of the autumn there is no ovary at all ; in the re- 

 producing larvae of the spring-time rudimentary ovaries or testes, 

 as the case may be, exist ; the young are not, however, produced 

 from these, but from germs in close connection with the fat- 

 body. In the larvae that go on to metamorphosis the ovaries 

 continue their natural development. It would, thus appear that 

 the fat-body has, like the leaf of a Begonia, under certain circum- 

 stances, the power, usually limited to the ovaries, of producing 

 complete and perfect individuals. 



Owing to the minute size and excessive fragility of the Gall- 

 midge flies it is extremely difficult to form a collection of them ; 

 and as the larvae are also very difficult of preservation, nearly 

 every species must have its life-history worked out as a special 

 study before the name of the species can be ascertained. oSTot- 

 withstanding the arduous nature of the subject it is, however, a 

 favourite one with entomologists. The number of described and 

 named forms cannot be very far short of 1000, and each year sees 

 some 20 or 30 species added to the list. The number of un de- 

 scribed forms is doubtless very large. The literature of the subject 

 is extensive and of the most scattered and fragmentary character. 



The Cecidomyiidae have but little relation to other Nemocera, 

 and are sometimes called Oligoneura, on account of the reduced 

 number of wing-nervures. Their larvae are of a peculiar type 

 1 NaturUst. Tidslcr. (3) viii. 1874, p. 34, pi. xii. 



