DESTROYERS OF APHIDES. 105 



of these creatures are armed with a singular mandible, 

 furnished, like a trident, with three points, with which 

 they transfix their prey. They lie at their ease under a 

 leaf or upon a leaf, surrounded by such hosts of Aphides, 

 that they can devour hundreds without changing their sit- 

 uation. (Plate x., figs. 7, 8, 9, Scava pyrastri.) 



(420.) Various hymenopterous insects are great des- 

 troyers of Aphides. There are some genera which deposit 

 their eggs in the bodies of the Aphis ; the egg grows and 

 becomes a maggot, which eats up the creature, avoiding, 

 however, the vital parts till the last. The Aphis when 

 attacked by this parasite swells up, assumes a globular 

 form, and at length dies and remains adherent to the leaf. 

 Aphides in this state are to be found on every plant, and, 

 indeed, upon almost every leaf which is affected with the 

 insect. In a few days after the death of the Aphis, the 

 inclosed creature eats a little circular hole and comes forth 

 a winged insect. The insects which thus destroy the 

 Aphides by thousands are called Ichneumons, but how 

 many species there may be which actually attack the 

 Aphis I am ignorant. I have figured two which have 

 escaped from Aphides in my own possession. (Plate x., 

 figs. 3, 4.) 



(421.) These insects are very minute, and may be 

 known at once from the winged Aphides by the total want 

 of resemblance in every particular. 



Curiously enough these creatures again have their 

 parasites ; for other Hymenoptera, the ChalcididcB for 

 instance, deposit their eggs in the maggot of the already 

 punctured Aphis ; and thus we have an Aphis with a 

 maggot within its body eating it up ; and lastly, a maggot 

 within this maggot devouring that also. I have figured an 



