376 DIPTERA. 



larva descends to the ground and moults there. Harris states 

 that "it is shorter, somewhat flattened, and more obtuse 

 than before, and is of a deeper yellow color, Avith an oblong 

 greenish spot in the middle of the body. In this state, which is 

 intermediate between the larva and pupa states, which has by 

 Dr. Fitch been termed the "embryo-pupa," and by us "semi- 

 pupa," the insect spins a minute silken cocoon, which, ac- 

 cording to Dr. Fitch, is smaller than a mustard seed and 

 remains in the ground through tlie winter, situated at the 

 depth of an inch beneath the surface. In the next June 



they are transformed to pupa?, 

 with the limbs free. When about 

 to assume the adult state the 

 pupa works its way to the surface 

 in June and July. Its chief para- 

 site, I*, tipulm, which in Europe 

 destroys great numbers of the 

 midge, is allied to the Flatygaster 

 error Fitch (Fig. 135). 



It is evident that deep plough- 

 ing in the fall or spring will destroy many of the insects, and 

 grain sown after the 15th or 20th of May, in New England, 

 will generally escape their attacks. 



The wings of the Hessian-fly are blackish ; those of the D. 

 tritici are transparent. This last species is orange colored, with 

 long, slender, pale yellow legs, and the joints of the antennae 

 are twenty-four in number in the male, and twelve in the fe- 

 male. 



The Cecidomyia rigidm Osten Sacken (C. salicis Fitch) forms 

 a gall surrounded by the dry and brittle terminal bud at the 

 end of the twigs of the willow. The single larva discloses the 

 fly early in the spring. The bright yellow larva of C. grossu- 

 laricB Fitch, causes the gooseberry to turn red prematurely' and 

 become putrid. The pupa of C. pini-inoph is supposed by 

 Osten Sacken to be coarctate, the larva fastening itself to a 

 pine leaf and remaining motionless until the resinous exuda- 

 tion resulting from its attacks hardens, forming a cocoon-like 

 pupa case or puparium. 



Mr. Walsh describes in the " American Entomologist," vol. i, 



