ii.] WHITE AND COLOURED STREAKS. 47 



of butterflies and moths, as you may see by turning 

 over the illustrations of any monograph of the group. 

 They exist among the hawk-moths, as, for instance, 

 in the humming-bird hawk-moth ; they occur in many 

 butterflies, as, in Arge galathea, which feeds on the 

 cat's-tail grass; and in many moths, as, for instance, 

 in Pyrophila tragopoginis, which feeds on the leaves 



FIG. 38. Arge galathea. 



of the "John Go-to-bed at Noon" (Tragopogon). But 

 you will find that the smallest caterpillars rarely possess 

 these white streaks. As regards the second point also, 

 the streaks are generally wanting in caterpillars which 

 feed on large-leaved plants. The Saty rides, on the 

 contrary, all possess them, and all live on grass. In 

 fact we may say, as a general rule, that these longi- 



