Insects Injurious to Agriculture. Ill 



than five species of plant lice. One of the most common 

 infests tlie tender leaves of tlie apple, tlie Aphis Mali, Fab. 

 This species is green, egg-shaped, one-tenth of an inch in 

 length ; it is either with or without wings. They are provided 

 with two spurs, or nectaries, which originate near the center 

 of the body. These nectaries secrete a fluid as sweet as honey. 

 So astonishingly prolific is this insect, that the increase of one 

 single egg, it has been estimated, in seven generations, would 

 be 729 millions! If it were not for the good offices of those 

 animals which prey upon plant lice, every thing green on the 

 face of the globe, would, in a short time, be covered with these 

 voracious insects. They crowd as thick as they can stand, 

 their long suckers inserted into the succulent young shoots 

 and leaves, pumping up the juice. If disturbed, they jerk up 

 their bodies in a comical way and emit, from their nectaries, a 

 shower of honey, apparently to bribe the intruder with this 

 sweet fluid. Not unfrequently they kick up their hind feet in 

 unison, impelled by an excess of animal spirits, from very joy 

 of existence. 



The history of this species is extremely interesting. In the 

 spring, as soon as the young leaves appear, the eggs hid away 

 in the crevices of the bark, hatch. The young creep to the 

 extremity of the branch and fasten on the young shoots. In a 

 few days the louse is fully grown. All the eggs laid in 

 autumn produce wingless females, and these females do not 

 lay eggs, but bring forth livi7ig young which are also females. 



The young when first born are milk white, but change in a 

 few hours to the color of the parent. In a very few days 

 these young lice produce living progeny also. And so on for 

 from fifteen to twenty generations, each individual louse pro- 

 ducing from five to ten each day, all without the presence of a 

 single male ; for in fact there is not a male in existence ! A 

 few winged females appear occasionally, which take wing and 

 plant new colonies. Thus goes on this remarkable form of 

 reproduction till fall, when there apj)ears a brood of winged 



