PLANT LICE 



which has no distinct head but from which is protruded 

 and retracted a pair of strong, dark hooks. Watch one 

 of these things as it creeps upon an unsuspecting aphid; 

 with a quick movement of the outstretched forward end 

 of the body it makes a swing at the fated insect, grabs 

 it with the extended hooks, swings it aloft kicking and 

 struggling, and relentlessly sucks the juices from its 

 body (Fig. 105). Then with a toss it flings the shrunken 

 skin aside, and repeats the attack on another aphid. This 

 heartless blood-sucker is a maggot, the larva of a fly 

 (Fig. 106) belonging to a family called the Syrphidae. 

 The adult flies of this family are entirely harmless, though 



Fig. 106. Two common species of syrphus flies whose larvae feed on aphids. 



(Enlarged about j>4 times) 



A, Allograpta obliqua. B, Syrphus americana 



some of them look like bees, but the females of those 

 species whose maggots feed on aphids know the habits 

 of their offspring and place their eggs on the leaves where 

 aphids are feeding. One of them may be seen hovering 

 near a well-infested leaf. Suddenly she darts toward 

 the leaf and then as quickly is off again; but in the moment 

 of passing, an egg has been stuck to the surface right 

 in the midst of the feeding insects. Here it hatches 

 where the young maggot will find its prey close at hand. 

 In addition to these predacious creatures that openly 

 and honestly attack their victims and eat them alive, 

 the aphids have other enemies with more insidious methods 

 of procedure. If you look over the aphid-infested leaves 



[177] 



