58 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 1 



with a straight base and with the apex 

 divided by a ventral incision into two large 

 lobes. Female genitalia, fig. 226: eighth 

 sternite projecting far beyond lateral lobes, 

 the apex rounded ; lateral lobes short and 

 somewhat ovate ; ninth segment with a some- 

 what vasiform, sclerotized, internal struc- 

 ture in addition to other membranous parts. 



The few Illinois records for this species 

 are scattered from the extreme northern 

 portion to the southern tip of the state. 

 The species is Holarctic, its distribution on 

 this continent extending southeastward to 

 Quebec, Wisconsin and Illinois. It has been 

 taken in a variety of habitats, and the rec- 

 ords indicate an adult emergence which 

 continues through the warmer months of 

 the summer. 



Illinois Records. — Golconda: April 17, 

 1930, Prison & Ross, 1 9. Homer: July 6, 

 1927, at light, Frison & Glasgow, 1 5 . 

 Savanna: June 2, 1942, at light, H. 

 Hersey, S S , 6 5. North of Wadsworth, 

 Des Plaines River: July 7, 1937, Frison & 

 Ross, 1 <5 . Waukegan: July 16, 1938, 

 Ross & DeLong, 1 9 . 



Neureclipsis validus (Walker) 

 Polycentropus validus Walker (1852, p. 100) 



cf. 



9. 



Hydropsyche dubitans Walker (1852, p. 113) 

 Polycentropus signatus Banks (1897, p. 30) 



This species has not yet been taken in 

 Illinois but has been recorded from On- 

 tario and western New York. 



Polycentropus Curtis 



Polycentropus Curtis (1835«, pi. DXLIV). 

 Genotype, by subsequent designation of West- 

 wood (1840, p. 49): Polycentropus irroratus 

 Curtis. 



Many of the species included under this 

 genus were formerly placed in Plectrocne- 

 mia and Holocentropus. The characters of 

 the larvae and pupae, as well as certain 

 characters of the adults, indicate that these 

 species together form a single unit as con- 

 trasted with other generic groups in the 

 family. I am making no attempt at this 

 time to judge the validity of either Plec- 

 trocnemia or Holocentropus; the study of 



nents, as well as a critical study of the 

 genotypes, will be necessary before the 

 names can be applied even to subgeneric 

 categories of North American species. 



About 25 species are known in North 

 America, of which 9 have been taken in 

 Illinois. Many of the species are rare but 

 widely distributed, and it is probable that 

 further collecting will yield new state rec- 

 ords in this genus. 



KEY TO SPECIES 



Larvae 



The following larval key is based on relative 

 characters and few species. For these reasons it 

 should not be used indiscriminately for specific 

 identifications. It is of considerable use for 

 separating to species larvae in a particular habitat 

 of known taxonomic composition, and it should be 

 used primarily for this purpose. 



1. Basal segment of anal appendages with 



setae fairly short and distributed 

 uniformly over ventral surface, fig. 



228 2 



Basal segment of anal appendages with 

 setae longer and grouped in two 

 lateral linear areas, fig. 228 3 



2. Spots on upper part of frons definite 



and forming an angle, fig. 230 



cinereus, p. 67 



Spots on upper frons indefinite and 

 forming a straight line or even arc, 

 fig. 231 centralis, p. 64 



3. Head almost uniformly brown, spots 



present but of only a slightly differ- 



228 



Fig. 228. — Polycentropus cinereus larva, 

 lobes of tenth segment, ventral aspect. 



Fig. 229. — Polycentropus interruptus larva. 



larvae of the species from various conti- lobes of tenth segment, ventral aspect 



