[ 4 *> ] 
which I found by divers Trials to be a very a&ive 
Acid, and which, among other Proprieties it has in com- 
mon with true Acids, fenlibly foftens the Glue of the 
Cafe. It remains now to fhew, that this Liquor 
is not only of Ufe to the Caterpillar , but is alfo 
that very Diftolvent which enables the Butterflie to 
cut its Way through : And this I am not without 
Hopes of being able to compafs. 
A Notion adopted by Dr. Boerhaave *, that there 
are no true Acids in Animals, except in the Stomach 
or Inteftines, renders this little Difcovery of the more 
Concern. 
IV. We have feen from the foregoing Obfer- 
vation, that Caterpillars , though one of thofe In* 
feds the Structure of which has been moft fearched 
into, have yet fomething ftill new to prefent in this 
refped. And I fhall further add, that I have dif- 
covered in thefe Infeds a Part of fome feemingCon- 
fideration, which is a fort of Nipple, or flefhy Protu- 
berance, placed near the Head, under the Firffc Ring; 
which is commonly concealed in the Infide of the 
Body, but is forced to fhew itfelf by fqueezing the 
Infed. This Nipple, or Protuberance, which at firft 
I only found lingle in feveral Caterpillars , I have 
iincc met with in others double, and even quadruple ; 
as in that lingular horned Caterpillar of the Willow , 
which I have already mentioned, and this with fome 
remarkable Varieties. However, they are not all 
provided with them : I have not found them as yet, 
for Inftance, in thofe of the Firft Size, that is to fay, 
the very large ones, nor in thofe that are very hairy. 
* Praxis Medica. Element* Chem. 
But 
