152 



INSECT TRANSFORMATION 



In paired pouches of this cavity, reaching back to the brain, 

 which lies in the hind thoracic region of the larva, are found 

 the imaginal discs for the eyes (Fig. 86 A e) and feelers 

 (Fig. 86/), which appear on the surface during the pupal 

 stage when the aforementioned pouches become everted 

 (Fig. 86 B C). 



H 



f 



W 



w 



B 



FIG. 86. 



A, Anterior region of muscoid maggot in longitudinal section 

 (diagrammatic), showing imaginal discs (B, brain ; H, inpushed 

 head region ; e, eye ; /, feeler ; W, forewing ; w, hind- 

 wing ; r, 2, 3, legs). B, The same in last stage, with legs 

 Cii Ifr 's) incipiently jointed and partly outpushed (p, disc 

 of proboscis). C, Formation of pupa by outpushing of head- 

 capsule with appendages and legs. A, from Carpenter, " Liie 

 Story of Insects " ; B, C, from Comstock, " Introduction to 

 Entomology." After Kowalevsky, Van Rees, and Lowne. 



The legs of pupa and imago are formed from buds or discs 

 growing in pouches directed inwardly from the body-wall of 

 the thoracic segments of the larva (Fig. 86 A, i, 2, 3). These 

 leg-buds increase in complexity as their segmentation becomes 

 apparent through a partial division of the originally simple 

 bud and the lengthening of regions at first telescoped into one 



