THE HIDDEN TYPE OF WING-GROWTH 129 



and the young larvae are hatched about a fortnight later. 

 They have a firm, broad head followed by thirteen body-seg- 

 ments whose cuticle is flexible and wrinkled but tough ; each 

 segment carries on either side a tuft of short bristles ; but at 

 the tail-end the tufts are long and prominent, projecting on 

 either side of the larva. As the grub increases in size through 

 its series of moults it becomes relatively longer in proportion 

 to its breadth, while the bristles appear far less prominent. 



FIG. 73- 



a, Crane-fly (Tipula oleracea) ; b, Larva (" leather-jacket " grub) of Tipula. 

 X 2. a, from Carpenter, " Life Story of Insects " ; b, after Comstock, 

 " Introduction to Entomology ". 



When fully grown (Fig. 73 b) the larva of a large crane-fly is 

 about 4omm. (i? inches) long, greyish in colour with black 

 spots, the tough cuticle (which has suggested the name of 

 ' leather-jackets " for these grubs) strongly wrinkled so that 

 the segmentation is greatly obscured. The best guide for out- 

 ward distinction of the segments is found in the minute bristles 

 arranged in pairs on the tergal and sternal areas. The head, 

 hard and firm but narrow in proportion to the body, has a pair 



9 



