Entomology of the Illinois River. 231 



very fine; dorsal and ventral areas of abdomen 

 strongly but rather unevenly striate. {lineola 

 group.) 

 Upper and lower thirds of prothoracic lateral area stri 

 ated, middle third smooth, without striae; only no- 

 ticeable marking a fleck of light brown in front of 

 the outer end of each dorsal false foot. ..species {a). 

 Middle third of prothoracic. lateral area striated like 

 the rest. 

 Upper thoracic lateral lines, at least of mesothorax, 

 accompanied by pale brown opaque stripes of pu- 

 bescence, which are slender, not dilated posteri- 

 orly, lateral edges of thoracic dorsal areas di- 

 verging [as in Fig. 47] lineola. 



Lateral lines of thorax without color or pubescence. 



costalis. 

 Lateral shining striated areas of pro thorax short, not 

 more than half as long as dorsal area, thoracic late- 

 ral darker stripes present, [atratus group.) 

 Lateral stripes of meso- and metathorax slender, pale 

 brown, scarcely dilated at posterior ends, lateral 

 edges of their dorsal areas diverging. [Fig. 47.] 

 Lateral striation of prothorax scarcely finer than 



that of mesothorax nigrescens^ stygius. 



Lateral striation of prothorax microscopically fine 

 and opaque; that of mesothorax much coarser, 



distinct and shining species (5). 



Lateral stripes of meso- and metathorax dark brown 

 in adult, dilated posteriorly on each segment, so 

 that the lateral edges of the dorsal areas become 

 parallel behind middle of segment; lateral stria- 

 tions minute and subopaque except in upper 

 , spaces on meso- and metathorax ; markings dis- 

 tinct at ail ages, annuli well developed. [Fig. 50.] 



atratus. 



