230 



INSECT TRANSFORMATION 



of the third and fourth abdominal segments are wanting, those 

 of the fifth and sixth serve with the thoracic legs for locomo- 

 tion. As the Erastria caterpillar grows it adds fresh scales to 

 its case, which it carries about continually and beneath which 

 it finally spins its cocoon and pupates, after biting a hole 

 through which it can afterwards emerge as a moth. 



Our consideration of this caterpillar leads naturally to a 

 fresh aspect of the surroundings of young insects the varied 

 means by which they secure shelter and protection from 

 enemies. Active, armoured larvae of predaceous habit are pro- 

 tected to a great extent by their firm exoskeleton and their 

 power of rapid motion. In the earlier section of this chapter 





FIG. Il6. 



a, b, ventral and dorsal views of the coccid-eating caterpillar of the Moth 

 Erastria scitula (/), the segments are numbered and the prolegs indicated 

 (p) ; c, side view of the caterpillar showing casing of scales in section ; 

 d, side view of case ; e, pupa, x (a, b, c) 3 ; (d, c, /) 2. From Riley (after 

 Rouzaud), " Insect Life", VI. 



(pp. 205, 210) examples have been given of many caterpillars 

 and grubs which feed by tunnelling in timber or mining in 

 leaves or becoming enclosed in galls, thus lessening the risks of 

 their lives by their hidden places of living. Many caterpillars, 

 both of moths and saw-flies, which are too large to live between 

 the two skins of a leaf, roll the edges of leaves together and 

 secure them by silken threads ; thus they may be said to use 

 their food-supply as a habitation, or to construct edible dwell- 

 ings for themselves. Well-known examples of this habit are 

 afforded by the caterpillars of the Green Tortrix moth (Tortrix, 



