OF WASHINGTON. 343 



entering the last segment from below; first segment slightly wider than 

 the metathorax, shorter than the following segments, anterior and pos 

 terior angles equally rounded; segments two to seven subequal in length, 

 diminishing in width, sides successively more arcuate, with hind angles 

 gradually more produced, becoming on the seventh segment reflexed 

 acuminate points; eighth segment longer than the preceding, with mar 

 ginal explanations reduced to carinae, produced above in an obtusely 

 rounded convex tip, and terminating in a .pair of large valvular spiracles 

 which resemble the nostrils of a seal; beneath, a transverse, trapezoidal, 

 slightly convex plate narrowed posteriorly; anal stylets as long as the 

 eighth segment measured dorsally, stout, tapering to a blunt point, de- 

 flexed, inserted beneath the dorsal prolongation of the last segment, base 

 deeply cleft, enclosing the anal opening. 



Stigmata obsolete, represented by small chitinous buttons placed close 

 to the anterior angles on the side margins of each ventral segment, be 

 ginning with the mesothorax and ending with the seventh abdominal 

 segment; two active spiracles on the eighth segment are terminal and 

 placed close together. 



The body is very strongly chitinized above, with deep sutures 

 on the dorsum, into which the anterior edges of the segments are 

 deflected from a sharply defined submarginal line. This line 

 marks the limit to which the dorsal plates can overlap when the 

 body is contracted ; in this position the head and tail are in the 

 same straight line, the explanate lobes on the sides overlap 

 broadly, the body is regularly fusiform, tapering rapidly behind, 

 and the form resembles a silphid of the first group (Silpha, Nec- 

 rophorus, etc.) When distended, however, the side lobes become 

 widely separated, the form elongates greatly, and the appearance 

 of the larva becomes caraboid. The simple ventral folds are not 

 capable of distending as much as the dorsal sutures; 'the body, 

 therefore, tends to arch downwards at the extremities ; thus full- 

 fed or distended larvae are strongly curved. 



The color varies in different specimens from piceous to testa 

 ceous ; when darkly chitinized the dusky mottlings or bands are 

 more or less obscured. In dark specimens also smoky patches 

 appear on the face of the ventral segments. The ventral surface 

 is entirely glabrous, but the convex upper surface shows, under a 

 lens, a sparse pubescence consisting of hooked bristles which 

 retain particles of dirt and lime precipitated from the water, 

 although this was not observed to form a solid coating as it does 

 upon many of'the adult beetles. 



The larva lives, with the imago, along the sides of rapid moun 

 tain streams, and, although submerged, evidently does not wander 

 far beneath the surface. It was especially abundant in the 

 eddies, in dark places, where it clung to floating sticks and wil 

 low catkins, or crawled slowly among small stones at the water's 



