148 HYMENOPTERA. 



for the cause of this wholesale destruction, we shall find 

 that it is occasioned by a multitude of small caterpillar- 

 like larvae, furnished with twenty feet, of a pale-greenish 

 colour, covered with numerous rows of little black tuber- 

 cles, each of which bears a small hair at its summit ; some- 

 times a thousand or more will inhabit a single bush, which 

 is of course soon stripped of every green leaf; in about 

 ten days these voracious larvae have attained their full 

 growth, when they descend into the ground beneath the 

 scene of their, ravages, enclose themselves in a small 

 cocoon, and undergo their transformation into a pupa. In 

 this condition they remain for a fortnight, when they 

 emerge in the perfect state. The fly thus produced is a 

 little Saw-fly (Nematus Grossularice), which in its turn 

 becomes the parent of another host of destructive goose- 

 berry grubs. It deposits its eggs along the course of the 

 principal veins, on the lower surface of the leaf, where 

 they are placed like rows of minute beads. The pupae 

 proceeding from this second brood pass the winter in the 

 earth, and the perfect insects do not emerge from them 

 before the month of March in the following year. 



The Cuckoo Flies (Ichneumon) are so called because 

 they lay their eggs in the interior of other insects, at 

 whose expense their progeny are nourished. For this 

 purpose the females are provided with a boring apparatus, 

 somewhat resembling a long tail, called their ovipositor, 

 by means of which they implant their eggs in the backs 

 of their victims, just as a gardener would set potatoes in 

 the ground. The female, when about to lay her eggs, 

 may be seen flying about with restless industry in search 

 of the larvae or pupae of other insects, or even spiders, to 

 which she is about to intrust the support of her family. 

 No matter where they are hidden, under the bark of trees, 

 or in cracks and crevices, she is sure to find them out, and 

 goon succeeds by means of her long ovipositor in piercing 

 their flesh, and depositing an egg in the interior of their 

 bodies, and occasionally she repeats the operation several 

 times. In process of time the eggs are hatched, and the 

 larvae of the Ichneumons find abundant food in their strange 

 domicile. By this proceeding the hungry but sterile 

 caterpillars are prevented from changing into the prolific 

 butterfly, and thus the world is defended against their 

 insatiable voracity. 



The Gall Flies (Cynips). These insects, too, are fur- 



