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 Satyridce, on the 

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

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



