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No. 145 ] 
upon flowers. These flies drop their eggs, one in a place, upon 
leaves and twigs which are infested with plant-lice, so that their 
young may have their appropriate food immediately around them 
the moment they require it. One can seldom inspect many in¬ 
fested leaves without meeting with one or more of the eggs of 
these flies scattered around among the lice—little white smooth 
oval bodies, much like the eggs which the hot fly glues to the 
hairs of horses’ fore-legs. From them a maggot hatches which 
in its motions will remind one of a leech or blood-sucker. It has 
no eyes, and consequently cannot see in which direction to crawl 
in search of its food; but fixing the hind extremity of its body to 
the surface of the leaf, it reaches as far as it is able to stretch it¬ 
self and feels around first upon- one side and then upon the other. 
If nothing is discovered it moves along one or two steps and again 
feels all around, until finding a plant-louse it at once fixes its 
tiny mouth at the slender-pointed anterior end of its body to its 
prey, having such power of suction as not only to hold the louse 
from escaping but to tear it away from its attachment and raise 
it up in the air wholly away from the surface of the leaf. The 
louse sprawls its long legs about in a vain endeavor to touch some 
support to enable it to escape. Its body is soon perceived to be di¬ 
minishing in size, the worm sucking out the fluids which it con¬ 
tains, and in a minute’s time, or less, nothing of it remains but 
an empty shrivelled skin. These Syrj hus-worms are of various 
colors, almost transparent and watery, or white, or greenish, and 
commonly clouded or spotted, particularly in the centre of their 
bodies, with more opake white, yellow, taw'ny or red, and their 
skin is so thin and transparent that the circulation of the fluids 
within may be distinctly seen even with the naked eye in the 
larger worms. Some of them have two cylindrical processes like 
little straight horns jutting out from the hind partof their bodies . 
One or more of these worms may almost always be met with 
wherever a colony of plant-lice is located, and one medium sized 
worm will consume a hundred of these insects in an hour. The 
ants do not appear to molest them, but the aphis-lions, as already 
remarked, devour them with avidity. When the worm has com¬ 
pleted its growth it fixes itself to the surface of the leaf or the 
bark, and contracts to a shorter oval form; its skin becomes hard 
