98 INJURIOUS AND USEFUL INSECTS 



bore, is not found in any saw-fly, where the abdomen is 

 always broad at its base. Saw-flies take their name from 

 a pair of remarkable appendages, carried by the female on 

 the under side of the extremity of the abdomen. These 

 answer to the ovipositor of the cockroach or the sting of 

 the bee ; but they are true saws in mechanical design, and 

 employed in cutting incisions upon twigs or leaves, in which 

 the eggs are afterwards laid. In the gooseberry saw-fly the 

 saws are not really such ; no cut is made in the leaf, and 

 the blades are only used to grasp the eggs. The common 

 saw-fly of the rose-tree may be watched by anyone who desires 

 to see the saws in action. 



There are usually three broods of gooseberry saw-flies in 

 the course of one summer. Eggs laid in autumn produce 

 larvae which do not proceed at once to pupate, but remain 

 for weeks or months underground as resting larvse, coming 

 up as flies only in the following spring. In the spring-brood 

 the numbers of the sexes are about equal, but in the autumn 

 brood the females greatly predominate. An unfertilised 

 female lays eggs readily, but these eggs always produce males. 

 This observation can be readily confirmed by hatching out 

 a female pupa, and then keeping the fly under a bell glass. 



The numbers of this destructive insect are subject to one 

 very important natural check; they are greatly infested by 

 ichneumons. After a series of years, during which the bushes 

 have been regularly stripped of their leaves, it will be found 

 by a close observer that the larvse produce in ever-increasing 

 numbers ichneumons instead of saw-flies. Then the saw- 

 flies fall off to such an extent that none can be found in 

 a wide district which was a few years before completely 

 devastated by them. 



Various remedies for the attacks of this insect have been 

 proposed. I have found nothing so effectual (except the 

 ichneumons) as searching the bushes about once a month 

 in summer, and removing every leaf which has eggs on it. 

 The operation is not too laborious, and it produces a marked 

 effect. A garden once cleared is not quickly overrun again, 

 as the flies change their quarters with difficulty. Some have 

 found it a good plan to remove the surface soil during winter, 

 and bury it in a deep hole. The resting larvae are thus de- 

 stroyed. The fresh soil from the hole is spread beneath the trees. 



