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doino- a similar injury by similar methods, but differing- especially 

 in life history. For the purposes of this article they need not be 

 particularly disting-uished, since the treatment of nursery stock 

 must be the same for both. 



If apple stock has been infested by the leaf aphis the preced- 

 ing- year, the fact will be shown at shipping- time, in fall or spring-, 

 by the presence on the tips of the twigs of minute, slender, oval, 

 shining- jet-black eggs fastened, perhaps in considerable numbers, 

 to the bud scales or the surface of the bark, or lodged in crevices 

 and on roughened places. These eggs will batch in early spring-, 

 and the young will commence at once to suck the sap from the un- 

 folding leaves, arresting- their growth and causing them to curl. 

 Considerable injury may thus bo done to the young tree, prevent- 

 ing- the tree growth of the twigs and making- a scrubby thicklv 

 tufted tip to each infested branch. The tree is thus prevented 

 from making a suitable season's growth, and its market value is 

 greatly reduced. 



The plant-lice themselves are small sluggish green insects, 

 thickly clustered on the buds and the under sides of the leaves, and 

 often attended by ants, which run actively up and down infested 

 trees, visiting colonies of the plant-lice for the purpose of lapping- 

 up the sweetish tUiiils which they give forth. Several generations 

 of these plant-lice arc produced ihiring a single season, of which 

 two are peculiar— the first and the last of the year. The lirst gen- 

 eration is the only one which hatches from an egg; all are females, 

 ami none of them have wings. The succeeding- generations are 

 born alive. All except the last are composed of females only, and 

 many individuals of these g-enerations may have wings and a con- 

 siderable power of tlight. The last generation of the year contains 

 both sexes, which pair, produce eggs, and perish. The two species 

 above referred to dilTer in the fact that the tirst mentioned, Ap/iis 

 //ui/:, spends the entire season on the apple, while the second leaves 

 the tree with the appearance of the third generation, resorting to 

 grasses and grains, and returning to the apple only in autumn to 

 produce the egg-laying generation, the last one of the year. 



It is practically impossible to destroy the egg-s of the plant- 

 louse, and to keep nursery stock free from it. The insects must be 

 destroyed in fall while they are on the trees but before the eg-gs are 

 laid. This period will vary according to season and latitude, being 

 of course the later the farther south one groes and the longer the 

 summer season lasts. In the latitude of central Illinois most of the 

 eggs are laid in September and October. 



