245 



of this broadened larva, or whether the skin is completely exuviated in 

 the transformation. 



I hope that those who have opportunity to capture beavers will en- 

 deavor to obtain the much-desired pupa, and I shall be most glad to 

 communicate with or to receive specimens from any one having such 

 opportunity. 



Fig. 50. — Platypsyllus castoris, ultimate larva: a, dorsal; b, ventral view; c, head from beneath; d, 

 tarsus ; e. tarsal claw (after Riley). 



Platypsyllus castoris. — Ultimate Larva — Length about 2.4 mm ; 

 greatest diameter about 1.2 mm . Nirmiform, flattened, narrowest at tho- 

 racic joints and broadest at middle of abdomen. Color grayish white, 

 with brownish, chitinous markings. Head pale brown, peculiar, project- 

 ing from joint 1, subtriangular, flattened, occiput without structure, face 

 and vertex completely ventral ; the mandibles resting on the proster- 

 num, ratber stout and 2 toothed ; clypeus very large, triangular; an- 

 tennae very smaii, 3-jointed, inserted in front of the lateral angles of the 

 clypeus, the basal joint rather large, circular, flattened disc-like, the 

 second joint minute, as long as broad ; the terminal joint much longer, 

 slender, cylindrical, and bearing a stout bristle at tip; labrum transpar- 

 ent and membranous; palpi apparently 4 jointed (not distinctly made 

 out) the terminal joint cylindrical, about one-half longer than wide and 

 truncated at tip; just outside the antennae are two black ocelli and 

 several piliferous raised points. Legs rather short, stout, drawn in over 

 the sternum; the tarsi spinose, long, 1-jointed, bearing but a single, 

 long, quite straight claw, with two long, movable spines at base ; tibiae 

 with but a few spines near tip. Dorsally, the prothorax is twice as 

 long as the other joints, which are subequal in width, and the trans- 

 verse brown markings include the prothorax, except a narrow posterior 

 band, a narrow posterior border across each of the joints (obsolescing 

 on 10, 11 and 12); a median subrhomboidal spot and a subdorsal nar- 

 rower, somewhat paler spot near the anterior margin of each of joints 

 2-11. The posterior half of each joint is also beset with numerous pale 

 brown granulations (obsolete on 11 and 12), but without a trace of hair. 

 Ventrally, the thoracic joints are much lengthened, the femora show 

 15035— Nos. 7 and 8 4 



