. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. LIFE HISTORY. 13 reproduction of the winged migrants of both the spring and the fall generations. The stem-mothers are very prolific, as shown in Table III, one aphis being capable of populating several leaves in a very short time. NUMBER OF GENERATIONS ON ALTERNATE HOST. Mr. Franz Remisch, of Saaz, Bohemia, who observed the emergence from the winter eggs, obtained two generations on plum. The writer did not observe the emergence of the first generation, but during the spring only two generations were found on pr
. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. LIFE HISTORY. 13 reproduction of the winged migrants of both the spring and the fall generations. The stem-mothers are very prolific, as shown in Table III, one aphis being capable of populating several leaves in a very short time. NUMBER OF GENERATIONS ON ALTERNATE HOST. Mr. Franz Remisch, of Saaz, Bohemia, who observed the emergence from the winter eggs, obtained two generations on plum. The writer did not observe the emergence of the first generation, but during the spring only two generations were found on prune, the second one being winged. In Bulletin 160 of the California experiment station Prof. W. T. Clarke reports the appearance of winged aphides 14 days after the first wingless insects were observed. This would be sufficient time for but one generation to mature, and it is very probable that there are only two generations upon the prune in the Pacific region. MIGRATING FORMS. The winged or migrating aphides, except for the pres- ence of two pairs of relatively large, delicate wings, some dark spots on the thorax, and a slightly more slender body (fig. 3 and PI. I, fig. 1) differ fit tie from the wingless form. They appeared at Perkins, Cal., May 15 and were present there and at Santa Rosa until June 15. Five belated individuals were observed at Perkins the latter part of July, but the migrations had taken place by the 20th of June. MIGRATORY ACTIVITIES. These winged aphides, which mature on the plum, are the first migrants. They are weak fliers, but when aided by a light wind may travel some distance. Their progeny, the wingless viviparous females, which are the most common forms found upon the hopvines throughout the season, are incapable of migration from one vine to another except where two vines come into contact so that the aphis. Fig. 2.—The hop aphis (Phorodon humuli): Windless viviparous female. Greatly enlarged. (Original.). Please note that these images are extra
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