STATES OF INSECTS. (Larva.) 205 
bewildered, retire to any small hole on the surface of the 
earth, covering themselves with dead leaves, moss, or the 
like, or to the chinks of trees, or niches in walls and other 
buildings, or similar hiding-places. Many penetrate to 
the depth of several inches under ground, and there form 
an appropriate cavern by pushing away the surrounding 
earth; to which they often give consistence by wetting 
it with a viscid fluid poured from the mouth. The larvee 
of other insects undertake long and arduous journeys in 
search of appropriate places of shelter. Those of flesh- 
flies, now satiated with the mass of putridity in which 
they have wallowed, leave it, and conceal themselves in 
any adjoining heap of dust. The grubs of the gad-fly 
(Estrus) creep some of them out of the backs of cattle, 
in tumours of which they have resided, and suffer them- 
selves to fall to the earth; while others, which have 
fed in the stomach of horses, quit their hold, and by a 
still more extraordinary and perilous route are carried 
through the intestines the whole length of their nume- 
rous circumvolutions, and are discharged at the anus. 
And without enumerating other instances, various aqua- 
tic larvee, as that of a common fly (Helophilus pendulus), 
&c. leave the water, now no longer their proper element, 
and betake themselves to the shore, there to undergo 
their metamorphosis. 
Most of these, having reached their selected retreat, 
require no other precaution; but another large tribe of 
larvee have recourse to further manceuvres for their de- 
fence before they assume the pupa. Those of the aphi- 
divorous flies (Syrphus, &c.), of the various lady-birds 
(Coccinella), and tortoise-beetles (Cassida), &c. fix them- 
selves by the anus with a gummy substance to the leaves 
