330 NEW YORK STATE MUSEUM 



KKY TO FA3IIL,IES OF NEMATOCEROUS DIPTERA 



Larvae 



1 Mandibles opposed, with the jaws mov- 



ing in a horizontal plane; when the 

 mouth parts are rudimentary, the larva 



has 13 segments and is peripneustic^ (2) N e m a t o c e r a 



Mandibles parallel, their motion in a verti- 

 cal plane; if the motion is obliquely 

 inward, then the head is not sharply 

 differentiated from the first thoracic 

 segment B r a c h y c e r a 



2 Larva with fully differentiated head, nou- 



retractile, which contains the first gan- 

 glion and sometimes the eyes, perip- 

 neustic or amphlpneustic,- with breath- 

 ing tube or tracheal gills (?,) Tribe E u c e p h a 1 n 



Larva with only a " jaw capsule " (Kie- 

 fer kapsel) (14) 



3 Terrestrial forms, living in the earth, in 



inibbish, under bark, or in fungi.... (4) 

 Aquatic or semiaquatic (G) 



4 Larvae without thoracic prolegs {v\) 



With thoracic prolegs. Living under bark Ce r a t o p o g o n 



5 Body bristly; head usually with eyes B i b i o n i d a e 



Body not bristly, head usually without 



eyes •. . . . ]\I y c e t o p h i 1 i d a e 



6 Prolegs at least on fourth and fifth seg- 



ments (i. e. on first two abdominals) (7) 

 No prolegs on these segments (S) 



7 Spiracles on the first and last segments, 



with tracheal gills, and a very long 



membranous breathing tube P t y c h o p t e r i n a e 



No long respiratory tube; larva swimming 



in a U-shape D i x i d a e- 



8 Body flattened, onisciform, and usually 



with suckers underneath (<.») 



Body more or less cylindric, without suck- 

 ers on the intermediate segments. . .(10) 



9 The segments alternating small and large, 



the out lino of the body, serrate. Liv- 

 ing in rapid flowing streams B 1 e p h a r o c e r i d a e 



The segments gradually larger at the mid- 

 dle of the body, becoming smaller 



again toward the posterior end P s y c h o d 1 d a e- 



10 With thoracic prolegs (13) 



Without thoracic prolegs (11) 



'Spiracles confined to the median segments. The Chironomidae usually 

 have jaws Miiicli move in olilique planes. 

 ^Spiracles confined to the first and last segments. 



