THE HIDDEN TYPE OF WING -GROWTH 143 



as the cocoon of the small turnip-eating caterpillar (Plutella 

 maculipennis). The pupa of a white butterfly (Pieris, Fig. 33), 

 or a Swallow-tail (Papilio) has the cocoon reduced to a pad of 

 silk to which the cremaster is anchored, and a supporting 

 girdle-thread around the thorax. Among the brilliant vanessid 

 butterflies the pupa is without this latter remnant, and hangs 

 head downwards from the silken tail-pad which alone represents 

 the cocoon. 



FIG. 83. COCOON OF SILK MOTH (Callosamio. promethea) IN LONGITUDINAL SECTION. 

 Natural size. After Comstock, " Introduction to Entomology ". 



A remarkable structure for the protection of the pupa, is 

 the puparium, characteristic of many families among the 

 Diptera or two-winged flies, especially such as the blue-bottle 

 group whose larva is a maggot. This puparium (Fig. 76, 7) 

 is the hardened and modified larval cuticle, which, after separa- 

 tion from the underlying tissue is not shed, in accordance 

 with the usual process at pupation, but becoming firm in 



