Entomology of the Illinois River. 265 



disks of the segments. On the third segment it is 

 especially dilated, always darker in color, and more 

 or less confluent with the adjoining dark lines, which 

 are also darker here, so that a blackish X-shaped 

 spot is formed more or less conspicuously. On the 

 other segments it is often nearly obliterated, so 

 that a narrow^ dorsal pale stripe is formed between the 

 first pair of dark lines, but never between the second 

 pair as is the case with the dorsal stripe in 0. cincta. 

 This first pair of dark vittae are the broadest; exterior 

 to them the pale vittae are obsoletely indicated, but 

 always visible at the sutures. At the posterior margin 

 of the eleventh segment the middle pair of pale vittae 

 invariably end, and the three upper dark vittae unite 

 npon the last segment in a dorsal band, narrowest and 

 blackish at its anterior fourth, and widening greatly 

 to near its apex. The second pair of dark vittae curve 

 inward from the bas^ of the last segment towards the 

 narrow part of the middle stripe, and beyond this are 

 usually more or less widely interrupted, the second and 

 third pairs of pale vittae then uniting in a broad pale 

 stripe in sharp contrast with the middle one. Three or 

 four of the segments preceding the last are bordered 

 posteriorly by a fuscous band. Beneath, six nearly equal 

 parallel dark vittae, sometimes nearly or quite obliterated, 

 more or less broken up on the last segment; lateral 

 margin pale, with a dark point in the middle on each 

 segment. Impressed sutural and lateral blackish points 

 as in cincta, the lateral ones ringed with blackish and 

 more conspicuous, especially those beneath and on the 

 last segment above. Surface finely granulated, sparsely 

 short-pilose above and below at the middle of each 

 segment. Spiracles brown, more distinct than in cincta^ 

 present on segments 1 and 4-10, plainly absent on the 

 meta- and mesothoracic segments. 



Head small, light brown, a dark longitudinal stripe 

 through each eye, middle lobe very feebly or not at all 

 sulcate, clypeus not notched ; basal joint of antenna 



