68 



ENTOMOLOGY 



pupation. These cells degenerate in the pupa, and take no part in the 

 formation of the imaginal ornamentation." 



FiG. 91. Modifications of the hairs of bees. A, B, Megachile; C, E, F, Colletes; D, Chelos- 



toma. After SAUNDERS. 



Histology. The chitinous cuticula owes its existence to the activity 

 of the underlying layer of hypodermis cells (Fig. 90), a single layer, 



1111111 



PIG. 92. Section of antenna of a moth, 

 Saturnia, to show developing hairs, c, cutic- 

 ula; //formative cell, or trichogen, of hair; 

 h, hypodermis; t, trachea. After SEMPER. 



FIG. 93. Radial section through the 

 base of a hair of a caterpillar, Pieris rapce. 

 c, cuticula; /, formative cell, or trichogen; 

 h, hairj.fcy, hypodermis. 



ectodermal in origin. These cells, distinct in embryonic and often in 

 early larval life, subsequently become confluent by the disappearance 

 of the intervening cell walls, though each cell is still indicated by its 



