ii.] WHITE AND COLORED STREAKS. 47 



and moths. They come off just at the same angle as the 

 ribs of leaves, and resemble them very much in general 

 effect. They occur also especially in species which feed 

 on large-leaved plants, and I believe I may say that 

 though a great many species of caterpillars present 

 these lines, they rarely, if ever, occur in species which 

 live on grass ; while, on the contrary, they are very 

 frequent in those species which live on large-leaved 

 plants. It might at first be objected to this view that 

 there are many cases, as in the elephant hawk-moth, in 

 which caterpillars have both. A little consideration, 

 however, will explain this. In small caterpillars these 

 oblique lines would be useless, because they must have 



FIG. 36. Smerinthus ocellatns. 



some relation, not only in color, but in their distance 

 apart,- to the ribs of the leaves. Hence, while there are 

 a great many species which have longitudinal lines when 

 young, and diagonal ones when they are older and larger, 

 there is not, I believe, a single one which begins with 

 diagonal lines, and then replaces them with longitudinal 

 ones. The disappearance of the longitudinal lines on 

 those segments which have diagonal ones, is striking, 

 where the lines are marked. It is an advantage, because 

 white lines crossing one another at such an angle have 



