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[Assembly 
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 w'hen 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 larva 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 Ichneumon idas in the Order Hymenoptera. 
One branch of this family i • composed of species w T hich feed inter¬ 
nally upon plant lice. It consists of the genus named Jlphidius 
and other genera, of the group which is named Jlphidiides. 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 
wing d ant in ap| earance, may occasionally be discovered busily 
at work amons: 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 
