DIPTERA NEMOCERA. 



743 



,b 



and as they are gregarious and their respective mucous sheaths fuse to- 

 gether, whole colonies in bands or ropes several yards long may be seen 

 migrating. Mycetobia British, has terminal stigmata.* 



Fam. 3. Blepharoceridae. No discal cell on the iridescent wings. 

 Eyes divided into an upper half with large ommatidia and a lower half 

 with small. This family is European 

 and American. The flies hover with a 

 dancing flight in the air. The larvae 

 are very remarkable, and more like 

 minute Polychaets than maggots. 

 They cling to submerged stones by 

 means of a row of ventral suckers. 

 The pupa is also aquatic. Liponeura 

 is European, Blepharocera is common 

 in the cooler parts of N. America. 



Fam. 4. Culicidae. Antennae with 

 rings of hairs forming a dense plume 

 in the male. Mouth-parts conspicuous 

 and forming a piercing proboscis 

 (Figs. 376, 471, 472). Complex 

 nervuration (Fig. 366). This extensive 

 and widely distributed family com- 

 prises the gnats and mosquitoes, 

 neither of which terms has any precise 

 zoological significance. A mosquito 

 may perhaps be defined as a gnat 



a 



FIG. 475. Larva of Culex pipiens hang- 

 ing on to the surf ace- film by its drawn- 

 out respiratory tube, magnified, a 

 bunch of hairs on the head which sweep 

 food particles into the mouth ; ^respi- 

 ratory tube. 



that sucks blood, but it must be remembered that it is only the female 

 that " bites." The normal food of the Culicidae is plant- or fruit-sap, 

 and it has been suggested that a meal of blood is necessary before eggs can 

 be laid. This however can hardly be the case, as in the waste lands of the 

 north there must be countless millions of gnats which never get an oppor- 



a 



FIG. 476. Larva of Anopheles maculipennis hanging on to surface-film. a brush of hairs 

 on the head (which is reversed so that the ventral side is uppermost) which brush food-particles 

 into the mouth ; b respiratory plate ; c hairs which cling to the surface film. 3 dorsal 

 view of an abdominal segment showing the lateral hairs and the dorsal whorl of hairs : 

 2 a dorsal whorl very highly magnified (after Imms). 



tunity to taste blood. The eggs are usually dropped on the surface of the 

 water or on aquatic plants. The larvae breathe by a pair of stigmata 

 situated posteriorly. In the genus Culex these open at the end of a 



* A very remarkable scale-bearing Mycetophilid larva is described by 

 Nils Holmgren, Zeitschr. Wiss. ZooL, Ixxxviii, 1907, p. 1. 



