CLASSIFICATION OF INSECTS. 181 



CHAPTER III. 



OF THE CLASSIFICATION OF DIPTERA. 



658. IN the second class, Diptera, the metamor- 

 phosis, as in Lepidoptera, is amorphous. Larva 

 with minute corneous mandibles, moving hori- 

 zontally ; without articulate or prehensile feet ; 

 feeds on recent or decaying animal and vegetable 

 substances. 



659. Imago of Diptera with the parts of the 

 mouth variously developed ; the mandibles never 

 possessing the horizontal motion, or masticatory 

 power ; the fore wings fully developed ; the hind 

 wings undeveloped ; assuming the appearance of 

 small pedunculated knobs, and denominated hal- 

 teres or poisers ; tarsi five-jointed. 



660. Wheat-flies (Cecidomyites). Larva elon- 

 gate, feeds on the blossoms of wheat and other 

 grain, the leaves of plants, &c. causing excres- 

 cences. Pupa changes in the same situation, in 

 a tough case. Imago usually with moniliform 



