SCALE-WINGED INSECTS. 283 



ing and in adhering to branches of trees, or to any other 

 solid substance. Besides the little hooks on the pro-leg, 

 the bottom of its foot is so arranged as to act as a sucker. 

 The mode of walking or crawling is different in different 

 caterpillars. Those which have pro-legs on nearly all 

 the segments crawl on all the feet at once, moving the 

 body straight along. Those which, on the other hand, 

 have only a few pro-legs, manage in this way : making 

 firm hold with their six clawed legs, they bring the pro- 

 legs, which are at the other extremity of the body, close 

 up in rear of the true legs, thus arching the intermediate 

 segments upward ; and now, holding on with their pro- 

 legs, they thrust the anterior part of the body forward 

 its full length. By a repetition of these movements they 

 make a slow and measured progress. From this mode 

 of walking such caterpillars are caUed loopers, or geom- 

 eters, or measure-worms. Some caterpillars will stand 

 for hours on the pro-legs in the rear part of the body, 

 with the forward part of the body extending upward at 

 right angles to this rear part. 



480. The food of caterpillars is, with few exceptions, 

 vegetable. Some feed exclusively on one kind of plant, 

 as the Silkworm on the mulberry ; some feed on a cer- 

 tain class of plants ; and others on almost any kind that 

 they happen to find. Their hours of eating differ, some 

 eating only in the morning and evening, some all day, 

 and others only at night. All eat a great deal some 

 more than twice their weight in twenty-four hours. If 

 all animals should do this, the eatables in the world would 

 soon be devoured. The perfect insects eat but little, for 

 they do not grow any larger than they were when they 

 first emerged from the pupa state. The larvae, on the 

 other hand, as they eat much, grow much also. 



481. Caterpillars are of great service in furnishing a 

 very large proportion of the food of birds. " It is ascer- 

 tained," says Jaeger, " that a single robin or woodpecker, 

 and many others of the warblers, carry every day about 



