THE PEAK AND CHERRY SLUG. 99 



CHAPTER XVI. 



THE PEAR AND CHERRY SLUG. 



( Selan dria cerasi. ) 

 Order : Hymenoptera. Family : Tenthredinidce. 



This most destructive insect, when in the larval state, 

 is a small dark-green slimy caterpillar, infesting the leaves 

 of both pear and cherry trees, which they injure very 

 much by gnawing the epidermis off the upper portion of 

 the leaves, leaving the skeleton and the lower portion of 

 the leaves untouched. 



Trees, according to Harris, attacked by this pest "are 

 forced to throw out new leaves, during the heat of the 

 summer, at the end of the twigs and branches that still 

 remain alive. This unseasonable foliage, which should 

 not have appeared until the next spring, exhausts the 

 vigour of the trees and cuts off the prospect of fruit." 

 But this is not the only damage for which the Pear 

 Slug is responsible, as by destroying the epidermis of 

 the leaves (see Plate XL, Fig. 1) the blazing sun 

 of a Victorian summer is by this means enabled to 

 penetrate with its full force right into the centre of the 

 tree, thereby causing a shrivelling of the bark, scalding 

 of the fruit, and otherwise injuring the trees. 



The egg of this saw-fly is deposited in a cut made in 

 the leaf by the saw-like ovipositor of the female, and 

 Mathew Cooke tells us that as many as nineteen eggs 

 have been found deposited in one leaf. 



The larva (see Plate XL, Fig. 2) is, according to Harris, 

 u hatched from the egg in two days, and feeds upon the 

 leaves as described above. It attains its full growth 

 in from 20 to 25 days. During the time it is feed- 

 ing it exudes an olive-coloured slimy substance, which 

 covers the body and gives it the appearance of a small 

 tadpole. When it ceases eating it casts its skin and 

 slimy coat, and appears with a clear yellowish skin ; the 



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