1.39 
on the Habits of the Purple Emperor. 
of silk to fix their claws in ; they grew torpid, and changed their 
bright green colour, first to a very dark, afterwards to a dusty, 
and at last a yellowish brown colour, pale on the underside, and 
in this state seldom were seen to stir, except in mild weather. 
I do not know whether it was the dryness and closeness of the 
place, where my willow-tree was kept in a pot, which was a sum- 
mer-house without windows, or what other circumstance, that oc- 
casioned the loss of the brood, but they grew evidently leaner and 
weaker, and dried upon their places before the spring could re- 
fresh them. As I went soon after on my travels, I had no oppor- 
tunity of making a second trial to bring others up. But I believe 
the rest of their history may be safely supplied by supposing 
that they do not change their behaviour, and that they slip off 
their skin twice more as most caterpillars do. 
This I must mention however, that my caterpillars, after chang- 
ing their skin a second time, seemed too small to me to equal the 
bulk of the full-grown one I had seen before, by twice casting 
their skins. But this might be also the consequence of the dry- 
ness of the place they were kept in, and where they were deprived 
of the morning dew, which I endeavoured to supply by sprinklino- 
water over them with a brush. I am the more apt to believe this 
because several other sorts of caterpillars brought up under the 
same consequences [circumstances] came but to a very incon- 
siderable size, and afforded me the smallest moths of the kind I 
ever saw. 
There is another property of the purple emperor caterpillars 
which it will seem ridiculous to mention, but as I often and con- 
stantly saw them do it, I would not neglect relating any of the 
singularities of this insect. The excremental masses of these 
little animals seem to be of so tenaceous a substance, that they do 
not fall off as soon as they are excreted. Therefore, at every ex- 
cretion the caterpillar, bending its body, takes the excrement with 
its foremost feet, and then, lifting it as high as possible, causes it 
to fall beyond the tip of the leaf. 
These are all the remarks I made upon the caterpillar of the 
purple emperor, which has given me no small diversion in my 
leisure hours, which I applied wholly to the observing various in- 
sects. The drawings which I made of the several changes I have 
not now at hand, but some of the dried eggs and caterpillars I 
lately found among a few insects, which I thought worth taking 
along with me when I left Berlin, and which I left with some cu- 
rious in Holland. 
