372 



DIPTEEA. 



which produce gall-like excrescences inhabited by the larvae. 

 The Wheat-midge or Hessian-fly does not, however, produce 

 such an enlargement, while other larvae only produce a folding 

 of the leaf, swelling of a leaf-rib, or arrest the growth of a 

 bud or stalk. 



Before giving a special account of the Wheat-midge, so de- 

 structive to wheat crops, let us, with the aid of Baron Osten 

 Sacken's resume in the Smithsonian Monographs of North 

 American Diptera, Part 1, take a glance at the habits of the 

 family. As a rule the species prefer living plants, though sev- 

 eral species of Epidosis and Diplosis live in decaying wood, and 



C. fuscicollis Meigen 

 (?) has been reared 

 by Bouche from de- 

 caying bulbs of tulips 

 and hyacinths. 

 Others live under the 

 bark of trees, in the 

 cones of pines, or in 

 fungi. Each species 

 is, as a rule, confined 

 to a peculiar species 

 of plant. Some of 

 the larvae live as 

 guests or parasites 

 in galls formed by other Cecidomyiae. Thus C. acrophila and 

 C. pavida live socially in the deformed buds of Fraxinus ; and 

 Diplosis socialis inhabits the gall of Lasioptera rubi. The 

 larvae of some species of Diplosis are parasitic among the plant- 

 lice (Aphis) . Some of the larvae live on the surface of leaves, 

 C. glutinosa having been found by Osten Sacken living on the 

 surface of hickory leaves. 



The rather long, cylindrical eggs laid on the surface of 

 leaves, etc., are generally hatched in a few days, though this 

 period may be hastened or retarded by heat or cold. The 

 young larvae are colorless and transparent, with age becoming 

 reddish or yellow, or white. They are fourteen-jointed. a 

 supposed supernumerary joint being placed between the head 

 and the first thoracic segment. The last abdominal ring is 



278 - 



