Page:Insects - Their Ways and Means of Living.djvu/198



the tree depends for a stunted and yellowed. to spray if he has not The entomologist, young aphids on the there are three kinds differing slightly, but to a separate species.

proper start of its spring growth, is Now is the time for the orchardist already done so. however, takes note that all the apple trees are not alike; perhaps of them in the orchard (Fig. enough to show that each belongs When the first buds infested are

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F1ç. 95- Three species of young aphids round on apples in the spring A, the apple-grain aphis, Rhopalosiphum prunifoliae. B, the green apple aphis, lphis pomi. C, the rosy apple aphis, lnuraphis roseus

exhausted, the insects migrate to others, and later they spread to the larger leaves, the blossoms, and the young fruit. The aphids all grow rapidly, and in the course of two or three weeks they reach maturity. The full-grown insects of this first generation, those produced from the winter eggs, are entirely wingless, and they are all females. But this state of affairs in no wise hinders the multiplication of the species, for these re- markable females are able of themselves to produce off- spring (a faculty known as parthenogenesis), and further- more, they do not lay eggs, but give birth to active young. Since they are destined to give rise to a long line of sure- mer generations, they are known as the stem mothers. One of the three aphid species of the apple buds is known as the green apple aphis (Fig. 95 B). During the

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