82 ILUNOIS BIOLOGICAL MONOGRAPHS [400 



complete, segments 2 and 3 with cephalic parts distincty reduced to mere 

 lines, sometimes all four segments fused; larvapods always setiferous, with 

 8-11 setae on cephalic and lateral aspects and a single ventral glanduba; 

 glandubae conspicuous, cylindro-conical, at least twice as long as wide 

 at proximal end; spiracles usually not winged, if winged, rather indistinctly; 

 setae stiff, brown, arising from fleshy mound-like minute tubercles; in 

 younger specimens third abdominal segment with five annulets, annulets 

 1, 2, and 3 with stiff brown setae; glandubae obsolete; cuticle microscopi- 

 cally spinulate; larvae usually feed upon grasses. 



This generic description is based upon two identified and several un- 

 identified species. The known species can be separated as follows: 



SPECIES OF PACHYNEMATUS 



Head with narrow fuscous or blackish streak along epicranial stem and vertical furrows; 

 tenth abdominal tergum with a broad fuscous streak on the meson and the caudal margin 

 produced distinctly caudad and bluntly pointed, with many conspicuous glandubae; antennae 

 with four fused segments; annulation, (2, 1), 6, (3, 4, 5); larvapods with 7-9 setae on cephalic 

 and 1 seta on lateral aspect; subspiracular lobe with 5-6 setae and 1-2 glandubae; surpedal 

 lobe with 5-7 setae and 1-3 glandubae; body on dorso-lateral lines with narrow, interrupted 

 longitudinal fuscous, bands; head as wide as thorax; length, 20 mm. width of head, 2 mm.; 



on Carex; Y-150 subalbalus Norton. 



Head with narrow fuscous or blackish streak along epicranial stem and vertical furrows; 

 tenth abdominal tergum without a broad fuscous streak on the meson, the caudal margin 

 only slightly produced caudad, rounded, with many glandubae; antennae with four segments 

 not fused; annulation, (1, 2), 6, (3, 4, 5) ; larvapods with about ten setae on cephalic and one se- 

 ta on lateral aspect; subspiracular lobe with about six setae and a single glanduba; surpedal 

 lobe with six setae and three glandubae; head as wide as thorax; length, 16 mm.; width of 

 head, 1.6 mm.; on Carex; Y-177 repertus MacGillivray. 



Nematus Panzer 



Larvae comparatively small, length about 10 mm.; body cylindrical, 

 uniform in diameter thruout the entire length excepting the caudal end, 

 where it is tapering, dull green, apparently glabrous; annulation indis- 

 tinct; third abdominal segment with six annulets, annulets glabrous, 

 formula: 1, 5, 2, 6, 3, 4; thoracic legs normal in form; coxa usually fus- 

 cous on proximal half; larvapods small, diminishing in size gradually on 

 the caudal segments, not setiferous; ventral glands subequal in size to larva- 

 pods; tenth abdominal tergum without a pair of caudal protuberances, 

 with a notch dorsad of suranal lobe as seen in profile, caudal margin trun- 

 cate or slightly emarginate on the meson, not produced; suranal lobe with 

 several minute setae on ventral aspect; subanal lobe with moderately 

 numerous minute setae; abdomen with lateral lobes inconspicuously 

 swollen; head circular in outline, rounded in profile on dorsal half, front 

 flattened; ventral half of head with several longer and larger setae; dorsal 

 half nearly glabrous or with microscopic setae; vertex usually with a fuscous 



