128 NORTH AMERICAN INSECTS. 
Caterpillars very often inform us as to the properties of 
the plants upon which they feed; thus the Potato-worm 
(Sphinx Carolina) feeds only upon the different species of the 
night-shade tribe (Solanew); for instance, on the egg-plant, 
the potato and tomato-vine, etc.; the Asterias (Papilio as- 
terias) lives upon the leaves of the umbrella tribe (Umbelli- 
fere), as the parsnep, cicuta, parsley, caraway, anise, cel- 
ery, ete.; and the Danaus (Danaus plexippus) feeds only 
upon the different species of milk-weed. 
The excrement of caterpillars furnishes an excellent dye- 
stuff, and their bodies the finest of varnish. It is well 
known that the body of each caterpillar is provided with a 
glutinous substance, by which they are enabled to manu- 
facture their cocoons; and to obtain this they are collected 
in many countries in large quantities, and boiled in water 
until a greasy liquor is seen floating upon the surface. 
This oleaginous substance is skimmed off, and proves a 
valuable varnish. It is said that the Japanese use this to 
varnish their finest fancy articles. 
Raising caterpillars for the purpose of obtaining from 
them perfect butterflies or moths is not only an agreeable 
and instructive operation for young pupils in their leisure 
hours, but it has often been a very lucrative business. In 
Altona, in Denmark, I became acquainted with a gentle- 
man who raised in his conservatory several species of the 
large moths, natives of North America—as the Cecropia, 
Luna, Polyphemus, and Promethea—which he sold readily 
at two dollars apiece, and of which he raised on an average 
a thousand specimens a year. 
Caterpillars are of quite an important use to man as the 
principal food of birds, and the amount of good they do in 
yielding up their lives as nourishment for others would as- 
tonish one unaccustomed to reflect upon the subject, and 
really goes far toward compensating the injury they do to 
vegetation. There are at least 1200 species of lepidop- 
