28 



BULLETIN 67, UNITED STATES NATIONAL MUSEUM. 



coarctate pupa. The larvae of many forms live in water, or at least 

 in moist surroundings. 



The classification usually adopted for the flies is that of Nemocera 

 for those having long antenna?, and palpi of four or five joints. The 

 pupa is naked, not coarctate, and the larva? usually have a very dis- 

 tinct head. The Brachycera have very short antennae, and palpi 

 of one or two joints. The pupa is often coarctate, and the larva? 

 usually have no distinct head. The further arrangement of the 

 groups is very unsettled. The suborder Nemocera can be arranged 

 in three sections: 



(1) The Polyneura (family Tipulidse, or crane-flies (fig. 55),) are 

 known from all others by the V-shaped suture on the thorax. Their 



legs are excessively long 

 and fragile, and the 

 wings and abdomen are 

 also slender. The larva? 

 are slender, and often 

 occur in water or moist 

 places. Some, how- 

 ever, are abundant in 

 fields. 



( 2 ) The Nemocera 

 vera have verticels or 

 whorls of hairs on the 

 antenna?. They have 

 slender bodies and legs. 

 The larva? of the gall- 

 gnats (Cecidomyiidse) 

 often produce galls on 

 various plants. The 

 Hessian fly (fig. 56) and 

 wheat midge belong 

 to this family. The 

 Culicidse, or mosquitoes, have scales on their wings. The larva? 

 (fig. 141) are aquatic, and familiar to most people as "wrigglers." 

 Only the female mosquitoes can bite, and it is now known that several 

 species transmit disease. The Anopheles maculipennis carries 

 malaria, and the Stegomyia calopus (fig. 57) disseminates yellow 

 fever. The Chironomidse, or midges, with feathery antenna?, have 

 aquatic larvae, and the fungus-gnats (Mycetophilida?) , with long 

 coxa?, breed in fungi, under loose bark, and in manure and 

 decaying wood. 



(3) The Nemocera anomala includes several small families which 

 have no whorls of hairs on the antenna?, and in which the body and 



Fig. 56. 



-The Hessian fly, Mayetiola destructor: a, Fly; 6, 



(i, ( , /, ENLARGED PARTS. 



