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The Biology of the Bean Thrips 469 Hilgardia [Vol. 7, No. 12 wing, 0.784 mm; average length of hind wing, 0.740 mm; fore wing with one branched vein in the center of wing dividing at inner edge of dark band. Anterior branch becomes contiguous with costal vein and posterior branch continues distinct to center of white area near tip. Costal spines usually 20; number of spines on posterior fork of midvein variable, 5 to 7 ; number of hairs in fringe on hind margin of wing variable, usually 30. Fore wing grayish brown, darkest along veins; dark area in center of wing equal to about one-half of wing's length, basal fourth white, and distal fourth equally divided into light and dark areas, tip dark. Hind wing uniformly grayish brown, basal fourth light ; one longitudinal vein in center of wing becoming indistinct near base and not reaching t i p ; spines on costal margin about 32 in number ; number of hairs in fringe variable, usually 42 ; entire surface of wings covered with very fine hairs. Femora dark brown except at tips; tibiae with central portion dark brown, ex tremities yellow; fore tibiae somewhat lighter brown; setae distributed irregularly on tibiae and tarsi ; hind femora only with setae ; spines present also on lateral mar gins of head, prothorax, and abdomen ; ninth and tenth segments of abdomen with a row of long spines on posterior margins. Short, strong spines are present on pos terior-lateral margins of abdominal segments. Abdomen slightly broader than thorax, ovate, tapering sharply to last segment. Ovipositor visible under magnifica tion, extending up into eighth segment. Approximate length of ovipositor, 0.167 mm. Adult Male.-The male differs but slightly from the female; it is somewhat smaller in size, the abdomen tapers more gradually, and the terminal abdominal segment is more blunt (fig. 2, A). The coloration, markings, and setae are practi cally identical. Under magnification the reddish-orange testes may be seen suspended in the seventh and eighth abdominal segments. The external portions of the genetalia may be seen to extend slightly beyond the end of the abdomen.

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The insects known as thrips constitute an important group of crop pests deserving much more attention than has been given them in the past. The increasing demand for higher-quality fruits and vegetables, free from blemish, has directed attention to the silvering and small scars usually produced by the rasping-sucking feeding process of thrips. Also, during the dry seasons recently experienced in this state (1929)(1930)(1931)(1932)(1933)(1934),The adult male bean thrips. thrips injured many crops through defoliation and through bud and flower injury. During this period the gladiolus thrips, an entirely new species, became the most serious pest of gladiolus in North America. In southern California the greenhouse thrips has so increased out-of-doors on avocados and citrus that control measures have become necessary.Another major outbreak of the pear thrips has forcefully recalled to mind an old pest in this group. Likewise the bean thrips for some time known as injurious to beans, cotton, and alfalfa, has become of concern

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