Miscellaneous. 
317 
with a dark, longitudinal streak down the back, which is the dorsal 
vessel. They are long and slender (fig. h represents a group of four 
of them of the natural size, and fig. c one of them highly magnified). 
The body consists of thirteen segments, gradually but slightly 
tapering towards the head, the segments being armed at the sides 
with strong bristles. They are destitute of legs, but are nevertheless 
able to crawl along with great rapidity, using the parts of the mouth 
and the appendages at the end of the body in locomotion. When 
disturbed they writhe about in a serpentine direction, or coil themselves 
up spirally remaining for a short time immoveable, and thus easily 
escape observation. The head is small and conical, furnished with 
two short antennae composed apparently of two joints, the basal one 
being very short, and the outer one terminated by a bristle (fig. d re- 
presents the front of the head seen from above, very highly magni- 
fied) ; the mouth is furnished with two large brown horny jaws, point- 
ed in a slight hook at the tips (fig. c?**), and the lower part of the 
mouth seems to consist of a large fleshy somewhat bilobed lip, furnished 
with two very minute two-jointed palpi. I also observed a small 
semi-globular tubercle on each side of the head behind the antennae, 
which may be the rudimental eyes. The terminal segment of the 
body is furnished with two small deflexed hooks, preceded by a co- 
ronet of minute setae, and which are evidently employed in walking. 
When full-grown these larvae assume the pupa state, having first 
entirely voided the remains of their undigested food, as is the custom 
with other larvae. All the larvae which I kept encased themselves 
within a cocoon of a silky texture and of an ellipsoid form, of a 
whitish colour within and grayish externally, often covered with 
minute particles of the adjacent materials Rbsel, however, observed 
that some of the larvae underwent these changes without forming a 
cocoon. The pupa inclosed within the cocoon bears considerable 
resemblance to the perfect insect, with this difference, that the legs 
are folded close on the sides of the body, and the insect is inclosed 
within a thin pellicle, each of the limbs being covered by a distinct 
case ; of course during this period the insect remains quite inactive, 
but as soon as the period for its final transformation arrives, it 
stretches forth its limbs, and casts off the thin pellicle with which 
it had been covered, and then appears as a perfect flea. Figure e 
represents the pupa highly magnified, with the cast skin of the larva 
(fig. /) attached to the extremity of its body. 
