442 MOTIONS OF INSECTS. 
path that it may find it again; but thus, whenever the caterpillar falls or 
would descend from a leaf, it has a cord always ready to support it in the 
air, by lengthening which it can with ease reach the ground. Thus it can 
drop itself without danger from the summit of the most lofty trees, and 
ascend again by the same road. As the silky matter is fluid when it issues 
from the spinners, it should seem as if the weight of the insect would be 
too great; and its descent too rapid, so as to cause it to fall with violence 
upon the earth. ‘The little animal knows how to prevent such an accident, 
by descending gradually. It drops itself a foot or half a foot, or even less, 
at a time; then making a longer or shorter pause, as best suits it, it reaches 
the ground at last without a shock. From hence it appears that these 
Jarvee have power to contract the orifice of the spinners, so as that no more 
of the silky gum shall issue from it ; and to relax it again when they intend 
to resume their motion downwards: consequently there must be a mus- 
cular apparatus to enable them to effect this, or at least a kind of sphincter, 
which, pressing the silk, can prevent its exit. From hence also it appears 
that the gummy fluid which forms the thread must have gained a degree of 
consistence even before it leaves the spinner, since as soon as it emerges it 
can support the weight of the caterpillar. In ascending, the animal seizes 
the thread with its jaws as high as it can reach it ; and then elevating that 
part of the back that corresponds with the six perfect legs, till these legs 
become higher than the head, with one of the last pair it catches the 
thread ; from this the other receives it, and so a step is gained : and thus 
it proceeds till it has ascended to the point it wishes to reach. At this 
time if taken it will be found to have a packet of thread, from which, how- 
ever, it soon disengages itself, between the two last pairs of perfect legs." 
To see hundreds of these little animals pendent at the same time from the 
boughs of a tree, suspended at different heights; some working their way 
downwards and some upwards, affords a very amusing spectacle. Some- 
times, when the wind is high, they are blown to the distance of several 
yards from the tree, and yet maintain their threads unbroken. I witnessed 
an instance of this last summer, when numbers were driven far from the 
most extended branches, and looked as if they were floating in the air. 
Having related to you what is peculiar in the motions of pedate larve 
upon the earth and in the air, I must next say something with respect to 
their locomotive powers in the water. Numbers of this description in- 
habit that element. Amongst the beetles, the genera Dytiscus, Hydro- 
philus, Gyrinus, Limnius, Parnus, Heterocerus, Elophorus, Hydrena, &c. ; 
amongst the bug tribes, Gerris, Velia, Hydrometra, Notonecta, Sigara, Nepa, 
Ranatra, Naucoris ; afew Lepidoptera ; the majority of Trichoptera; Li- 
bellula, Aeshna, Agrion, Sialis, Ephemera, &c. amongst the Neuroptera ; 
Culew and many of the Tipularie Latr. from the dipterous insects ; and 
from the Aptera, Atax, some Podure, and many of the Oniscide, &c. All 
these, in their larva state, are aquatic animals. 
The motions of these creatures in this state are various. Some walk 
on the ground under water ; some move in mid-water, either by the same 
motion of the legs as they use in walking, or by strokes, as in swimming; 
others for this purpose employ certain lamina, which terminate their 
tails as oars ; ethers again swim like fish, with an equable motion ; some 
move by the force of the water which they spirt from their anus; others 
1 Reaum, ii, 875, 
