290 



— Abdomen with, at most, groups of setulse on the dorsum ; wing eases 



distinctly separated from sides of thorax, flaplike; the skin not 

 chitinous, collapsing after emergence of adult ; last segment of ab- 

 domen generally ending in two flattened leaflike organs which 

 are usually ciliated along their edges 3 



3. Thoracic respiratory organs consisting of two or three main stems 



terminating in many threadlike filaments Cliironomincp, pt. 



— Thoracic respiratory organs consisting of one simple stem which is 



diversely shaped in the different species 4 



4. Thoracic segments much distended, thoracic respiratory organs sit- 



uated well forward and generally swollen ; abdomen flattened, re- 

 sembling the pupae of Coretlirincv Tanypinm. 



— Thoracic segments slightly distended ; thoracic respiratory organs 



situated well forward, but generally elongated ; abdomen rounded, 

 resembling the ordinary form in Cliironomus . . CliironomincB, pt. 



IMAGINES 



1. Thorax not projecting over head, sternopleura not particularly en- 



larged nor descending much below apices of fore coxae ; antennae 

 in both sexes with 15 joints; medio-cubital cross vein absent; me- 

 dia with 2 branches; proboscis heavily chitini'?;ed 



C eratopogoniTUE. 



— Thorax distinctly projecting over head ; sternopleura much enlarged 



and descending considerably below apices of fore coxae; antennae 

 either with 15 joints in both sexes (Tanypma') or the female with 

 8 or less (Cliironominm) ; medio-cubital cross vein present or ab- 

 sent ; media simple or with 2 branches ; proboscis fleshy, not chi- 

 tinized 2 



2. Medio-cubital cross vein present; antennae in both sexes with 



15 joints Tanypincc. 



— Medio-cubital cross vein absent, or if that vein is present the an- 



tenna of the female with at most 8 joints CJiironomince. 



CERATOPOGONIN^ 



Larval, Characters 



The larvae of the terrestrial and semiaquatic forms of this subfam- 

 ily are readily separated from those of any other genus in the family 

 Chironomida: by the presence of very distinct, regularly arranged bris- 

 tles on the thorack and abdominal segments. In many instances some 

 of these bristles are lanceolate, or at times branched, and their arrange- 

 ment is invariably the same in the individuals of a species, while dif- 

 ferent species are, as far as now known, distinct in the disposition of 

 the bristles. The antennae are distinct, not retractile (PI. XVIII, Fig. 

 15), the mandibles are distinctly toothed, the teeth generally three in 



