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- 

 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 diif erentiated 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 E u c e p h a I a 



Larva with only a " jaw capsule " (Kie- 

 f er 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 bai-k Ce r a t o p o g o u 



5 Body bristly; head usually with eyes Bibionidae 



Body not bristly, head usually without 



eyes M y c e t o p h i 1 1 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 (Si 



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 D i x i d a e 



8 Body flattened, oniseiform, and usually 



with suckers underneath (!t) 



Body more or less cylindric, without Slick- 

 ers on the intermediate segments. . .(KH 



9 The segments alternating small and large, 



the outline of the body, serrate. Liv- 

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



10 With thoracic prolegs (13) 



Without thoracic prolegs (11) 



'Spiracles confined to the median segments. The Chirouomidae usii;illy 

 have jaws which move in oblique planes. 



^Spiracles confined to the first and last segments. 



