TWO INSECTS AFFECTING WHEAT AND BARLEY CROPS. 



325 



and slowly but surely so weakening the stalk that by the time (about 

 four weeks) of reaching full growth it gives way ^nd bends down to the 

 ground. 



The larva during the feeding stage is of a white colour, with a slight 

 greenish line down its back. 



Kemaining in the same position, the larva, having done feeding, 

 changes to a chestnut colour, the outer skin hardening in the straw. 

 This is the quiescent puparium stage (fig. 116), the one in which the 

 Hessian Fly was introduced into Great Britain and elsewhere. 



At this stage I would call particular attention to the fact that the 

 puparium has its head down and its mouth next the stalk, a position 



Fig. 116. — Section of fallen Barley showing the puparium of the Hessian 

 Fly in situ, (x 6 diam.) 



in which it would be impossible for the fly to emerge, as it would have 

 to penetrate the stalk ; and then, supposing that this was done, the fly 

 would be a prisoner within the hollow stem betw^een the two knots. 



Some entomologists, in their haste to account for all and everything, 

 have fallen into serious error in connection with the small chitinous 

 apparatus, termed the anchor process, on the third segment of the 

 mature larva found within the puparium- — a stage so different from 

 most other larval conditions on reaching maturity that a few words of 

 explanation may be of interest to those who are not entomologists. 



From the first appearance of the tiny larva of a moth or butterfly 

 to its perfect state, its transformations are nothing more than a constant 

 throwing-off of its outer skin ; after the last moult the pupa is evolved, 

 then the perfect insect. 



