. Circular. Insect pests; Insect pests. These multiply with astonishiug rapidity * for from live to twelve generations, carrying us in point of time to the hop-picking Fig. 3. -The Hop Plaut lonse, third generation on Plum—the generation which flies to the hop- enlarged ; head below at right—still more enlarged. There then develops a generation of winged females which fly back to the plum tree and give birth to the true sexual females (Fig. 4), which never acquire wings and never leave the plum tree. By the time this generation has matured, which involves but a few days, varying accor
. Circular. Insect pests; Insect pests. These multiply with astonishiug rapidity * for from live to twelve generations, carrying us in point of time to the hop-picking Fig. 3. -The Hop Plaut lonse, third generation on Plum—the generation which flies to the hop- enlarged ; head below at right—still more enlarged. There then develops a generation of winged females which fly back to the plum tree and give birth to the true sexual females (Fig. 4), which never acquire wings and never leave the plum tree. By the time this generation has matured, which involves but a few days, varying according to the temperature, belated winged individuals, which are the true males (Fig. 5), fly in from the hop fields. These fertilize the wingless true females upon the plum leaves and these soon thereafter lay the winter-eggs. Thus there is but one generation of sexed individuals produced and this at the close of the life-round—the fe- ^, . males wingless on i^lum trees; the males winged i^"^?^\ ( on hops. All intervening generations are com- The Hop Plant-louse, poscd of virgin fcmalcs only '(parthenogenetic). true, sexual female —en- m, . , . • , i i - , • . i • ,- litraed. This IS the invariable round ot the insect's Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Bureau of Entomology. [Washington, D. C. ] : The Division
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