138 
Dr. Pallas’s Observations 
lean a body could afford silk sufficient to line its way) ; when it 
comes to the extremity of the leaf, it begins to gnaw the edge of 
the leaf at a little distance from the top ; after the repast it retires 
to the very tip of the leaf, where it resides upon the rib on the 
upper side, with the head directed towards the stem of the leaf, 
resting itself with the fore-claws loosened and applied close to the 
body. This fashion the creature observes all the following time 
of its life. It gnaws the leaf on both sides to the bare rib, leaving 
the tip untouched, which it covers with a thick white web, to fix 
its claws in when it rests. When a leaf is consumed, it resorts to 
the next downwards. It feeds covering all its way with silk, and 
by these means, tying the leaf, which it takes possession of, to the 
branch. 
The yellow colour which they have when first hatched soon 
changes, as it seems by an effect of their food, to a pleasing green, 
a little whitish on the underside, and with the same roughness of 
skin and yellowish oblique lines on the back, which are observed 
in the full grown ones. 
When the period of slitting off their first skin approaches, the 
first joint of the body swells behind the head to a considerable, 
yet low, tumour ; they disengage themselves by casting off the old 
scull, and slipping off the skin like a serpent ; and now there ap- 
pears a head quite different in shape to what it had before, and 
such as we observe in the full-grown caterpillars. The horns on 
both sides round the body are a semicircular form, and occasion 
the forementioned tumours. As soon as the head is freed from 
the old skin, the horns begin to stretch and to rise to an erected 
situation, and, from short appendages, grow to slender and long 
horns, forked at the tip in the same manner as we see the wings 
of a butterfly. In some minutes the head has acquired its colour 
and solidity, and the new-born caterpillar turns itself to devour 
its cast-off skin, after which it returns to its usual food. 
The second casting of the skin is attended with the same cir- 
cumstances ; the horns of the new scull are convolved in the very 
same manner, and stretched, after being disengaged. At the se- 
cond renovation the figure of the horns is different from what it 
had been before ; they are shorter and not forked at the extremity. 
By this time the season grows cold, and the willow begins to 
lose its leaves, but those that were occupied by these little insects 
had their stalks thus fortified and tied with silk that they could not 
fall, but shrivelled up and dried. My little caterpillars, thus desti- 
tute of food, disposed themselves here and there on the underside 
of the branches, where they covered a little space with a carpet 
