METAMORPHOSES OF ALASKA COLEOPTERA 3^1 



as pronotum, transverse, not deflexed ; prosternum with a large 

 rounded schlerite between the bases of the anterior legs. 



Feet slender, elongate, sparsely armed beyond the coxse with small 

 short spines ; coxaj nearly as long as femora ; tibia two-thirds as long 

 as the femora; femora and tibiae densely ciliate above and below; 

 tarsi half the length of the tibiae; clafv^s short, unarmed. 



Abdomen tapering gradually from first segment to apex ; ninth seg- 

 ment three times as long as broad, truncate at apex, bearing distally a 

 pair of lamellate cerci which are densely ciliate; eighth and ninth 

 segments laterally with a row of long cilice. 



Described from larvce taken at Yakutat and Kukak Bay. The 

 transformation of this species takes place in the earth beneath stones 

 lying along the shores of the ponds inhabited by the larvae and adults. 

 The larvae resemble very closely those of the allied species Dytiscus 

 marginales L. and differ only in a few small details ; the body is more 

 convex than in the latter species, the posterior margin of neck Is emar- 

 ginate above and the furrow on the ventral surface of the neck is 

 strongly carinate. 



AGABUS TRISTIS Aub6. 



[Plate XXIII, figs. 3-6. ] 



Larva elongately ovate, acuminate behind, convex above, flattened 

 beneath, dorsal surface light brown mottled with yellowish, ventral 

 surface white. Length 12 mm. 



Head rounded, convex above, flattened beneath, delicately reticulate, 

 posterior angles broadly rounded; neck short, the sinus between the 

 latter and head deep ; frontal angles strongly produced, obtusely 

 rounded at apex ; clypeus transverse, rounded in front, bordered an- 

 teriorly with a row of delicate lamellate setae; frontal sulci faintly 

 marked, surrounding the epistoma, which is slightly convex, circular 

 and depressed in the middle ; sides of temples acutely carinate, the 

 margin serrate and spinulose. Mandibles slender, tapering, evenly 

 curved on both external and internal margins, apex rather sharp, suc- 

 torial orifice close to tip on inner surface. Antennae not half as long 

 as head, slender, setaceous, four-jointed, the joints successively 

 shorter. Ocelli six, arranged on an oval prominence situated on 

 the side of the head just behind the antenna ; the two anterior ocelli 

 are round, the remaining four more or less elongate. Maxillae elon- 

 gate, slender ; stipes twice as long as broad, external margin sinuate ; 

 galea consisting of a small, slender, finger-shaped joint not much 

 longer than the basal joint of the palpus; maxillary palpus reaching 



