194 KING AID [37 2 ] 



almost to apex of antennae, four-jointed, basal joint squarish in out- 

 line, the remaining joints successively shorter. Mentum exserted, 

 corneous, transverse, trapezoidal, three times as broad as long, an- 

 terior border straight and wider than at base ; labial palpi as long as 

 the second and third joints of the maxillary palpi combined, slender, 

 two-jointed, the first joint longer than the second; ligula absent. 



Pronotum a little longer than wide, broadly ovate, narrowed some- 

 what in front, angles rounded, convex above, finely reticulate, sides 

 distinctly margined. Mesonotum and metanotum transversely oval, 

 three times as wide as long, sides broadly rounded; sterna not 

 chitinized, folded. 



Legs slender, elongate, with numerous short spines ; coxae stout, 

 elongate, unarmed, femoral groove distinct, carinated ; femora as 

 long as coxae, more slender, compressed, sparsely setose; tibiae two- 

 thirds as long as the femora, sparsely setose ; tarsi nearly as long as 

 tibiae, claws long and slender. 



Abdominal segments gradually diminishing in size from the first to 

 the sixth ; dorsal scutes transversely oval, angles rounded ; segments 

 seven and eight are entirely corneous; eighth segment slender, 

 elongate, conical, bearing at apex two cerci that are about as long as 

 the last two segments of the abdomen ; the cerci are more or less 

 ciliated apically and at the nodes; segments six to eight are finely 

 tuberculate above ; spiracles in abdominal segments one to six are 

 situated at the lateral margins of the schlerites and are visible from 

 above. 



Pupa pure white ; front of face flattened, concave between the 

 eyes ; occiput transversely ridged, with a row of bristles extending 

 from one eye to the other. Length 8 mm. Described from larvae 

 and pupae found under a stone on the margin of a small pond near 

 the Muir Glacier. 



No description appears to have been published of the metamorphoses 

 of any of the American species of Agabus. 



BYRRHUS FASCIATUS Fabricius. 

 [Plate XXIV.] 



Larva pale brown, lighter between the schlerites; form elongate, 

 cylindrical; outline in side view a flattened curve. Length 18 mm. 



Head rounded, shining, globose, almost as broad as the pronotum, 

 heavily punctured and with scattered hairs on the front and vertex. 

 Clvpeus broadly transverse, trapezoidal, frontal margin truncate 



