lOS ^ATURAL HISTORY 



J\[ost caterpillars live singly upon the particular plant which sup- 

 plies their nourishment, but some species, especially the Bombycidae, 

 live in societies or families more or less numerous. In the latter case 

 they are all the offspring of the same insect which has deposited its eggs 

 in one place, and, when the young come forth, they live there in a kind 

 of nest or tent which affords them a common slieller. Some, whose or- 

 ganization is so delicate that they cannot endure contact with the exter- 

 nal air, fabricate a kind of case or garment of silk, which invests them 

 so that they only expose their head when feeding, and in this they un- 

 dergo tlieir changes. 



^Vith the exception of a great number of Tineidae, which live at the 

 expense of our furs, our wollen stuffs, upon skins and upon fatty sub- 

 stances, all catterpillars ked upon vegetable substances, and from the 

 grape to grains nothing escapes tliem, though most insects prefer feeding 

 upon green leaves. Next to these they prefer flowers. Plants the most 

 acrid and the most poisonous, such as the Euphorbias and Aconite, are 

 as eagerly eaten as the most insipid. 



For a long time it was believed that every species of plant nourish- 

 ed its peculiar species of caterpillar, but that error is now confined to 

 those utterly unacquainted with entomology. The same species some- 

 limes lives upon twenty different trees, and the same tree sometimes 

 nourishes more than fifty different species of caterpillars; thus, for in- 

 stance, the Lacquey caterpillars feed upon fruit and forest trees in- 

 discriminately. But whilst caterpillars are generally polyphagous, yet 

 in a great many cases they are intimately related to particular vegetables: 

 we find certain genera or certain groups of lepidopterous insects corres- 

 pontjing to certain families of plants. Whilst we know of no plant that 

 is not attacked by insects in its native place, theie are yet numerous in- 

 stances in which plants transported to another region entirely escape 

 these ravages. Thus a great many exotic trees transported to Europe 

 remain uninjured, though frequently stript of their leaves in their native 

 soil. But if a tree belongs to a genus found in the country to which it 

 has been transferred, it enjoys no such exemption. Thus all the pop- 

 lars and willows brought from North America are subject to the same 

 attacks as our indigenous trees of a similar nature. 



The ChrysaJis stale. 



When the caterpillar has reached its full size, it ceases to cat, as it did 

 when about to moult, it draws itself together, changes its color and be- 

 comes of a dull, livid hue : if it is of a gibbous form its lumps arc ab- 

 sorbed and disappear, and, after having found a suitable retreat, it throws 



