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as well as in the marked deviation from the previous stage, it recalls 

 the pseudo-pupa, or coarctate larva of the Meloids, and of some 

 other parasitic forms. I have but a single specimen and have not 

 been able to clearly make out the spiracles. One can but conjecture 

 as to whether the pupa proper is formed, either partially or wholly, 

 within the skin of this broadened larva, or whether the skin is com- 

 pletely exuviated in the transformation. 



I hope that those who have opportunity to capture beavers will 

 endeavor 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. 



a^ Z- 



a, dorsal ; h, ventral view ; c, head from beneath ; d, tarsus ; e, tarsal claw (original). 



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

 diameter about 1.2 mm. Nirmiform, flattened, narrowest at thoracic joints 

 'and broadest at middle of abdomen. Color grayish white, with brownish, 

 chitinous markings. Head pale brown, peculiar, projecting from joint i, 

 subtriangular, flattened, occiput without structure, face and vertex completely 

 ventral; the mandibles resting on the prosternum, rather stout and 2-toothed; 

 clypeus very large, triangular; antennae very small, 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 transparent and membranous; palpi apparently 4-jointed (not dis- 

 tinctly 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, i -jointed, bearing but a single, long, quite 

 straight claw, with two long, movable spines at base; tibite 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 transverse brown markings include the 

 prothorax, except a narrow posterior band, a narrow posterior border across 



