ORDER DIPTERA. 



87 



while the hind wings are represented only by a pair of small 

 knotted organs, called halteres. Their metamorphoses are com- 

 plete. 



The larv(B are footless "grubs," generally with a soft body, but 

 sometimes leathery or even nearly horny. Many of them possess 

 a distinctly marked head, which may contain ocelli^ but in the 

 majority the head appears as if it were simply one of the neigh- 

 bouring segments. 



Fig. 121. — Craspedia Coriaria. 



Their food generally consists of decayed animal and vegetable 

 matter, and thus they are very useful as scavengers, particularly in 

 hot climates. 



The larv(B frequently live in the substance upon which they 

 feed, while others reside in water, and many are parasitic. 



For the classification of the Diptera we owe much to that 

 eminent entomologist, Osten-Sacken, whose arrangement has been 

 here generally adopted. 



TABULAR VIEW 



OF THE 



PRINCIPAL FAMILIES OF THE DIPTERA. 



Tribe I. — Nemocera. 



Family i. Cecidomyiidse or Wheat Midges. 

 ,, 2. Mycetophilidce or Army Worms. 

 '\. Simuliidse or Sand P'lies. 



