51 
small pea, the larva writhes itself through, a ring or segment at a 
time, till arriving at the narrower part of its body it falls out, 
and tumbles to the ground, and seeking a convenient retreat be¬ 
comes a chrysalis. 
After leaving the abscess, and preceding their change, they 
contract themselves into a much smaller space, and assume a dif¬ 
ferent figure. See Plate II. fig. 4. They never change or throw 
off their skin, apparently, but the same serves them through their 
whole growth, and at length also forms the shell of the chrysalis, 
as in the other species of this genus. 
If we examine the sac which enclosed the larva beneath the 
skin, it appears formed of condensed cellular membrane, and is 
rough on the inside. The pus secreted is mostly of a yellow 
colour, and sometimes flows from the opening, and dries about 
the orifice. After the exit of the caterpillar the abscess disap¬ 
pears, and the wound in the skin closes up and is healed in a few 
days : but although the skin heals up on the exit of the larva, we 
may remark, that the union is not so firm as was the original 
skin, but is affected by a sort of agglutinating deposit, which 
afterwards on the skin being dried and hammered by the tanners 
gives way and cracks again in these places, shewing the union to 
have been of a less perfect nature than the original skin ; the 
succedaneous nature of the repair of broken skin, has been 
remarked by late physiologists, and we mention this fact as con¬ 
firmatory of their doctrine. 
The chrysalis is of a dark brown colour, and in figure some¬ 
what resembles the half of a walnut shell, being narrower at one 
end than the other, and flat on one side, and very rounded and 
convex on the other. See fig. 6. Those which I bred remained 
in the state of chrysalis from the latter end of June till about the 
middle of August, when the Fly appeared. I have, notwith¬ 
standing, observed full grown larvae in the backs of cows as late 
