GROWTH AND TRANSFORMATION 173 



characteristic of the '' free " pupa, as such a type is called. 

 The obvious presence, when the pupa is revealed, of wings 

 and other organs characteristic of the " imago " or perfect 

 insect confirms our impression that the pupal stage of the 

 life-history indicates a period of reconstruction and com- 

 paratively rapid change. But a knowledge of the processes 

 of animal growth in general leads the student to infer that 

 such profound changes could not be brought about without 

 previous preparation. So that we are led to expect that 

 wing-rudiments must be somewhere present in the cater- 



FiG. 46. — A, B, C, Stages in development of wing-bud (b) of a 

 Lady-bird Beetle (Hippodamia) , shown in section, c, cuticle (shown 

 in A only) ; e, epidermis ; s, sensory hair-cell ; i, trachea; fr, tracheoles. 

 X 100 (approx.). After Comstock and Needham, " Wings of Insects." 



pillar or other insect larva. They were indeed observed 

 more than a century and a half ago when P. Lyonet in his 

 great treatise (1762) on the caterpillar of the " Goat " 

 Moth (Cossus) sav/ two pairs of small white bodies lying in 

 the fatty tissue of the second and third thoracic segments. 

 He did not certainly recognise them as wing- rudiments, 

 but he pointed out that their number and position suggested 

 that such might be their nature. They are indeed the 

 wing-buds of the insect, lying hidden beneath the body- 



