401 



— Wings with distinct surface hairs; third vein ending appreciably 



farther in front of apex of wing than fourth ends behind it 



Tanytarsus (p. 484) . 



7. Wings with distinct surface hairs Metriocnemus* (p. 497). 



— Wings bare 8 



8. Thorax with a distinct longitudinal furrow ; antennae in both sexes 



short-haired and with 7 joints (2-|-5) . .Cluismatonotus (p. 499). 



— Thorax without median furrow ; antennjB of male wdth more than 7 



joints 9 



9. Apical portion of lateral arm of hypopygium not recurved, un- 



armed at apex on inner side (PL XXXVII, Fig. 16) 



Pseudochironomus] (p. 500) . 



— Apical portion of lateral arm of hypopygium recurved, generally 



armed on inner side at apex with one or more thornlike proc- 

 esses 10 



10. Legs conspicuously bicolored, black and white ; eyes hairy 



Cricotopus (p. 501 ) . 



— Legs not conspicuously bicolored, either black or brown, or if paler 



without sharply contrasted colors 11 



11. Posterior branch of cubitus conspicuously bisinuate (PI. XXXV, 



Fig. 9) Camptodadius (p. 507) . 



— Posterior branch of cubitus either straight or slightly sinuous 



OrtJiocladius, sens. lat. (p. 512) . 



N. B. The genera Tersesthes Townsend and Eutanypus Coquillett are unknown 

 to me. 



Key to Larv.t:| 



1. Eleventh segment wdth latero-ventral blood-gills, which are usually 



very long and situated low 2 



— Eleventh segment without blood gills 7 



2. Only one pair of blood gills on eleventh segment, situated high on 



side at posterior margin, and occasionally very short or even 



*Eurycnemu.9, which has been recorded from New Jersey, differs from Metrioc- 

 nemus in having the mesonotum conically produced in front, and the hind tibise dilated 

 and hairy. I have not seen Illinois specimens of this genus. A genus, Brillia, has 

 been erected by Kieffer for the reception of those species of Metriocnemus that have 

 the hypopygium with apical portion of lateral arm bifid. At least one American 

 species belongs to Brillia. 



tThis genus is intermediate between Chironomus and Orthocladius, resembling 

 the former in the structure of the hypopygium and the latter in venation and in having 

 the basal joint of the fore tarsi conspicuously shorter than the fore tibia?. The species 

 described under the name Chironomus pseudoviridis, n. sp., in this paper shows a much 

 closer approach to the typical Chironomus, and I therefore leave it in that genus 

 though the length of the basal joint of the fore tarsi is not equal to that of the fore 

 tibiae, and the hind tibia; have an apical spur instead of a comb of reguJar, closely 

 placed spinules. 



i Species without page number are not treated in text. 



