330 NEW YORK STATE MUSEUM 



KEY TO FAMILIES 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) Nematocera 



Mandibles parallel, their motion in a verti- I 



cal plane; if the motion is obliquely i 



inward, then the head is not sharply I 



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- 



neustic or amphipneustic,' with breath- | 



ing tube or tracheal gills (3) Tribe Eucephala j 



Larva with only a " jaw capsule " (Kie- i 



f er kapsel) (14) j 



3 Terrestrial forms, living in the earth, in ' j 



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



Aquatic or semiaquatic (6) , 



4 Larvae without thoracic prolegs (5) I 



With thoracic prolegs. Living under bark Ceratopogon 



5 Body bristly; head usually with eyes Bibionidae 



Body not bristly, head usually without 



eyes Mycetophilidae I 



6 Prolegs at least on fourth and fifth seg- i 



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



No prolegs on these segments .(8) i 



7 Spiracles on the first and last segments, 



with tracheal gills, and a very long \ 



membranous breathing tube Ptyehopterinae ' 



No long respiratory tube; larva swimming 



in a U-shape Dixidae ' 



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. 



