File:Economic entomology for the farmer and fruit-grower - and for use as a text-book in agricultural schools and colleges (1906) (14778066555).jpg

Identifier: economicentomo00smit (find matches)
Title: Economic entomology for the farmer and fruit-grower : and for use as a text-book in agricultural schools and colleges
Year: 1906 (1900s)
Authors: Smith, John Bernhard, 1858-1912
Subjects: Insect pests
Publisher: Philadelphia London : J.B. Lippincott company
Contributing Library: University of British Columbia Library
Digitizing Sponsor: University of British Columbia Library

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mes requires years to supply a miss-ing link in their life history. The differences between them arenot always well marked, and the tendency has been to recognizespecies as distinct when they feed on different food-plants. Thisbasis has proved erroneous, however, and now the wonder is tofind how many food-plants a single species may actually have. It has been mentioned that a number of plant-lice feed uponroots, and some species pass their entire life underground. Suchare the RhizobiincE, which sometimes become distinctly injurious,as, for instance, when they occur on the roots of lettuce, in green-houses-and out-doors. Sometimes they are found on the rootsof trees or shrubs, quite usually attended by ants, which provide 128 AX ECONOMIC ENTOMOLOd. for their distribution. As they never come to the surface, so faras we know, they are never winged, and are usually dull whitein color, or with a slight tinge of green. The body is coveredwith a whitish powder and lacks honey-tubes. Fig. 94.
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Phylloxera vastatrix.—a. unaffected rootlet of grape; b, rootlets with newly-formedgalls; c, same, with old and driedup tissue; dd, groups of the lice on roots and root-lets ; e,f, female pupa, from above and below; g,h, winged females; z, an antenna; j,oviparous wingless female and her eggs; k, root showing location of the eggs. An advance upon those root-living species is found in Phyl-loxera, which belongs with Chermes in a sub-family, Chermesina, THE INSECT WORLD. 129 distinguished by having only two discoidal veins on the fore-wings. The grape Phylloxera is known by reputation all overthe world, and its ravages in European countries have calledforth volumes of print. It has been thoroughly studied in ourown country by Dr. C. V. Riley, among others, and from hisworks the following life history is taken. The insect winters on the roots of grape, mostly as a youngwingless form. This starts growth in spring, rapidly increasesin size, and soon commences to lay eggs, the young from w

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