MAY FLIES AND MIDGES OP NEW YORK 251 



Pupa. The thoracic respiratory organs are simple, tube-like, 

 sometimes with enlarged extremities. Abdominal segments with 

 minute and short setae. The anal segment with 6 terminal setae, 

 three on each side. 



The larvae and pupae of O r t h o c 1 a d i u s do not seem to 

 differ from Cricotopus. 



Imago. This genus resembles Chironomus, from which 

 it is distinguishable in having the fore metatarsus a half or a third 

 shorter than the tibia. The last abdominal segment of the male 

 is much shorter than the preceding and is broader than long; the 

 claspers are short and broad, and usually white in color (pl.33, 

 fig.2). The legs are white and black annulate, the fore tarsi are 

 bare or covered with very short and inconspicuous hair (in an 

 exceptional case the male has bearded tarsi) ; the hind tarsi are 

 also usually bare. The halteres are always white or pale yellow. 

 Wings bare, the anal angle, particularly in the male, is promi- 

 nent; R 4+5 is straight or slightly btfnt at its extremity, the cross- 

 vein is a little beyond the middle of the wing; the cubitus is 

 forked, the base of the fork a little distad of the crossvein ; the 

 lower branch is straight or gently arched toward the hind mar- 

 gin ; the humeral crossvein is wanting or rudimentary. 



The species of this genus are all small (2 to 4 mm.) and with 

 black and yellow coloring, the dorsum of the thorax has 3 shin- 

 ing black stripes, which sometimes are so wide as to entirely 

 obliterate the yellow dividing lines, so that only the humeri remain 

 yellow. 



KEY TO SPECIES OF CEICOTOPTJS 



Larvae 

 a Sides of each abdominal segment with pencil of long hairs, pl.24, fig.9 



3. trifasciatus 

 aa Abdomen without such pencils 



& Middle tooth of the labium longer than the first laterals, pl.24, 



figs. 1. 2, 4 4. e x i 1 i s n. sp. 



&& Middle tooth about as long as the first laterals, pl.25, fig.22 



6. v a r i p e s 

 Pupae 

 a Pattern upon each abdominal segment in two wide transverse bands, 



resembling that shown on pl.25, fig.7 4. exilis n. sp. 



aa Not marked in this manner 



& Markings as shown on pl.24, fig.7; thoracic respiratory organs as 



shown on fig.8 3. trifasciata 



&& Dorsum uniformly covered with minute spines 6. v a r i p e s 



