. Economic entomology for the farmer and fruit-grower [microform] : and for use as a text-book in agricultural schools and colleges. Beneficial insects. AN ECONOMIC ENTOMOLOGY. Fig. Thrips tritici.—b, antenna ; c, a tarsus. The mouth structure is in some respects intermediate between that of the true bugs, as already described, and that of the man- dibulate type ; but there are no true mandibles, and the insects can- not chew their food, hence come naturally, for our purpose, into this order. The species of Thrips are often seriously injurious to vegetation. They sometimes attack onions in gre
. Economic entomology for the farmer and fruit-grower [microform] : and for use as a text-book in agricultural schools and colleges. Beneficial insects. AN ECONOMIC ENTOMOLOGY. Fig. Thrips tritici.—b, antenna ; c, a tarsus. The mouth structure is in some respects intermediate between that of the true bugs, as already described, and that of the man- dibulate type ; but there are no true mandibles, and the insects can- not chew their food, hence come naturally, for our purpose, into this order. The species of Thrips are often seriously injurious to vegetation. They sometimes attack onions in great numbers, puncturing the suc- culent leaves, and everywhere leav- ing a small yellow dot. As these increase in number the leaf loses vitality, the top itself turns yellow, and in serious cases the rich green of a normal onion field is changed to a peculiar, sickly yellow. The insect is yellowish when immature, and blackish-brown when the wings are developed. Cabbages sometimes suffer in a similar manner. The insects in this case are yellow, and congregate in large numbers on the lower side of the outer leaves, and as these become dry and wither they move to those nearer the centre. Grass is often attacked by them, and here they cause one form of what is known as "silver ; Wheat, oats, rye, and other grains are often victimized, and, indeed, there are few plants not liable to infestation, even tobacco appearing among the sufferers. These insects thrive best in hot, dry weather, hence become more dangerous as the plants are less able to resist them, and our effort must be in the direction of aiding the crop as well as destroying the insects. Contact poisons are indicated here, as against the true Hemiptcra., and either the kerosene emulsion, diluted ten times, or the whale-oil soap, one pound in four gal- lons of water, is satisfactory. Plenty of cold water, where it is available, acts very well on a small scale ; but no application is feasible on large fields o
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherphila, bookyear1896
