134 CHERRY. LEAVES — ICHNEUMON-FLIES. APHIDIUS. 



Syrphus flies are equally efficient in destroying this and all the 

 other species of plant-lice. In connection with our account of 

 those destroyers, all of which attack the aphides externally, it 

 was stated that there were others which live in the bodies of 

 these insects and thus destroy them. And we come now to pre- 

 sent to the reader some information respecting our American 

 species of these insects whose habits are so remarkable. 



It was anciently supposed that an Egyptian quadruped which 

 is named the Ichneumon had the habit of darting down the throat 

 of the crocodile when it was sleeping, and there remaining, feed- 

 ing upon the entrails of this reptile until it perished. This, how- 

 ever, has long been known to be fabulous. But among insects 

 there is an extensive group, resembling wasps and bees, which 

 possess this very habit which was formerly ascribed to the Ichneu- 

 mon. They in their larvae state reside within the bodies of their 

 victims, feeding upon them until they destroy them. They have 

 from this circumstance obtained the name of Ichneumon-flies, and 

 they form the Family Ichneumonim: in the Order Hymenoptera. 

 One branch of this family is composed of species which feed inter- 

 nally upon plant lice. It consists of the genus named Jlphidius 

 and other genera, of the group which is named Aphidiides. These 

 are all exceedingly small insects little exceeding the twentieth of 

 an inch in length, and mostly with black bodies variously adorned 

 with bright tawny yellow and pale sulphur yellow bands and 

 other marks. One of these small Ichneumon-flies, resembling a 

 winged ant in appearance, may occasionally be discovered busily 

 at work among a colony of aphides. With her long thread-like 

 antennae stretched out in front of her and rapidly vibrating, she 

 approaches an aphis and touches it gently, much like an ant when 

 nursing these creatures. By this slight touch she at once ascer- 

 tains whether the aphis has been previously visited. If it has 

 not she curves the tip of her abdomen forwards under her, punctu- 

 ring the body of the aphis and inserting an egg therein. She 

 then passes to another and another. From this egg hatches a 

 minute worm which resides within the aphis, subsisting upon the 

 juices which the latter extracts from the plant. Thus it grows 

 with the growth of the aphis, which furnishes the exact amount 



