ILEA. 
457 
beset with distant liairs, and furnished at the head 
with a pair of short antennre or tentacula, and at 
the tail with a pair of slightly curved forks or 
holders: their colour is white, with a reddish cast, 
and their motions <piick and tortuous. These larva3 
are very frequently found in the nests of various 
birds, and, in particular, of pigeons, where they 
fasten occasionally to the young brood, and sa- 
turate themselves with blood. In the space often 
or twelve days they arrive at their full growth, 
when they usually measure near a quarter of an 
inch in length: at this period they cease to feed, 
and, casting their skin, change into the state of a 
chrysalis, which is of a white colour, and of an 
oval shape, with a slightly pointed extremity, and 
exhibits the immature limbs of the included insect. 
The larvae are said to spin themselves up in an 
oval cotton-like covering before they undergo 
their change: this however is not always the case. 
After lying for the space of tw^elve days in chry- 
salis, the complete insect emerges in its perfect 
form. It now begins to exert its lively motions, 
and employs the sharp proboscis with wdiich Na- 
ture has furnished it in order to obtain nourisli- 
ment from the first bird or quadruped to wiiich it 
can gain access. The time required for the evolu- 
tion of this animal varies considerably according 
to the season of the year, and in the winter months 
is of much longer duration than the period above- 
mentioned j the egg scarcely hatching under twelve 
days, and the larvm lying nearly twdce the usual 
time in chrysalis. 
