HYMEXOPTEKA. 



147 



Avhich in some species serves for the deposition of 

 the eggs, but in others is connected with a poison- 

 bag, and forms a venomous sting. To this Order 

 belong 



The Saw Flies (Tenthredo). They derive their name 

 from a cin-ionsly-eonstructed instrmnent called an ovi- 

 positor, with which the female is provided. This con- 

 sists of a saw composed of two blades that work alter- 

 nately, by means of which she makes incisions in the 

 branches of plants, wherein she deposits her eggs. The 

 wounds thus made by the teeth of the sav^ frequently 

 cause the plant to swell into a fleshy mass resembling a 



Fig. 1 



SATv' OF SAW FLY. 



small fruit, in the interior of which the larvte find the 

 materials for their subsistence. The larvae very much 

 resemble caterpillars, from which, however, they are easily 

 distinguished by the number of their feet ; before changing 

 into nymphs, the false caterpillars enclose themselves in a 

 cocoon, in which they remain many months in their 

 caterpillar condition, only becoming changed into nymphs 

 a few days before their final conversion into Saw flies. 



In the spring-time of the year, when the bright leaves 

 of our gooseberry-bushes first make their appearance, they 

 are often devoured in a remarkable manner, even before 

 they have completely concealed the straggling spiny 

 branches. ^ If the injury stopped here, with the despolia- 

 tion of his gooseberry-bushes, the gardener might perhaps 

 put up with it without much grumbling; but unfortunately 

 the production of leaves and fruit are intimately connected, 

 and unless the branches are well clothed v/ith the former, 

 the crop of the latter will be very small. If we search 



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