INSECTS. 93 



caterpillars nine to eleven pairs. The head of the 

 latter is more rounded, while that of the former is 

 more flattened. The way in which caterpillars walk 

 depends upon the number of their legs. If this is 

 fairly large so that most of the segments of the 

 body are provided with legs, the whole body remains 

 tolerably extended during progression. But if the 

 number is small — as in the looper caterpillars, where 

 there are three pairs of thoracic legs at the anterior 

 end, and at the posterior end only a terminal pair of 

 legs (the caudal pro-legs) and another pair in front of 

 them — the middle legless region is strongly bent 

 during locomotion (Fig. 63). Hence the name 

 "looper." The loopers often bend their bodies in a 

 characteristic way. When at rest the hinder part is 

 coiled up spirally; but as soon as the animals are 

 alarmed they throw the hinder part of the body 

 upwards and forwards and even over the head. The 

 grubs (Figs. 66 and 69, left) have indeed, like the 

 caterpillars, a clearly visible hard head, but no charac- 

 teristic abdominal legs, or at most a pair of sucker 

 feet at the end of the body (wireworms). Thoracic 

 legs are present in several grubs (cockchafer larvae, 

 wireworms, leaf-beetles) ; in others (larvse of weevils 

 and fleas) they are entirely absent. Maggots are those 

 entirely footless insect-larvse which do not possess a 

 head clearly marked off from the rest of the body, 

 and the head-end of which is only to be recognized 

 by the presence of the mouth and mouth-parts. 

 PupcB are enclosed in a case which either only faintly 

 indicates the outline of the various parts of the adult 

 insect, or else closely surrounds every part of the 

 l)ody — wings, legs, antennae, and even the mouth- 

 parts and eyes. Pupae of the first kind are termed 

 oUectate (Fig. 60) ; those of the second, free (Figs. 



61,65), ^ , 



Many pupae are naked, others are surrounded by a 

 web (cocoon) spun by the larva (Fig. 60). There are 



