Natural History of Aphides. 63 



171 the same species. The most striking monstrosities are often 

 produced only by the minute female parent. 



Development. — It is well known that the Aphides are propa- 

 gated through many generations in a year ; that all those gene- 

 rations are born alive at one period by apterous and at another by 

 winged females ; that the presence of a male is not required, and 

 that the males appear only when, at the end of that enormous 

 multiplication, eggs are deposited by umvinged females. Not all 

 of them, however, have many generations, nor are all both ovi- 

 parous and viviparous ; most likely some genera are only vivi- 

 parous, some others only oviparous. Kaltenbach has based on this 

 difference a division into vivi -oviparous, viviparous, and oviparous. 

 Of the two latter we know at present very little. The vivi- 

 oviparous bear during the summer only living young, and infi- 

 nitely often ; in the autumn at the same time with the appearance 

 of the males, eggs are deposited, from which the female parents 

 of the next year are produced. This sometimes happens during 

 the winter, oftener in the next spring. The action of bearing in the 

 summer, as well as the deposition of the eggs in the autumn, can 

 easily and often be observed. They bear often fourteen or fifteen 

 times a day ; after the lapse of from four to ten days, the young 

 specimens begin to bear. In June we find often grandmothers and 

 grandchildren together ; the latter are then already often winged. 

 In the same brood there often occur winged and apterous speci- 

 mens ; the apterous are always sooner fertile. The deposition of the 

 eggs, which always causes the death of the specimen, takes place 

 in autumn, and always from apterous females. 



Copulation. — The act of it is seldom observed, the males 

 being so scarce and so small, and observation being seldom made 

 at the exact time it takes place, Bouche saw that the same male 

 copulated with from four to six females, one after another. 



Hibernation. — The Aphides hibernate generally in the state 

 of eggs ; sometimes the female parents survive the winter ; those 

 of the viviparous species always. Bouche saw whole colonies 

 hibernate, even males, which had not copulated. 



Importance in economy to Jields, gardens, and forests, — The 

 Aphides are in this respect very important ; they often cause 

 monstrosities and distortions of leaves, and are often very per- 

 nicious to the crops. The mildew of the grain crops and upon 

 peas is said by several authors to be the product of Aphides ; this 

 is, however, not likely. The number of Aphides is sometimes 



