330 NEW YORK STATE MUSEUM 



KEY TO FAMILIES OF NEMATOCBROUS 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 Brachycera 



2 Larva with fully differentiated head, non- 



retractile, which contains the first gan- 

 glion and sometimes the eyes, perip- 

 neustie or amphipneustic,^ with breath- 

 ing tube or tracheal gills (3) Tribe Eucephala 



Larva with only a " jaw capsule " (Kie- 

 fer kapsel) (14) 



3 Terrestrial forms, living in the earth, in 



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

 Aquatic or semiaquatic (6) 



4 Larvae without thoracic prolegs. ..... .(5) 



With thoracic prolegs. Living under bark Oeratopogon 



5 Body bristly; head usually with eyes Bibionidae 



Body not bristly, head usually without 



eyes Mycetophilidae 



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 Ptychopterinae 



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 (9) 



Body more or less cylindric, without suck- 

 ers on the intermediate segments. . .(10) 



9 The segments alternating small and large, 



the outline of the body, serrate. Liv- 

 ing in rapid flowing streams Blepharoceridae- 



The segments gradually larger at the mid- 

 dle of the body, becoming smaller 



again toward the posterior end Psychodidae 



10 With thoracic prolegs (13) 



Without thoracic prolegs (11) 



'Spiracles confined to the median segments. The Chironomidae usually 

 have jaws which move in oblique planes. 

 ^ Spiracles confined to the first and last segments. 



