Insect pests of farm, garden and orchard . so coveredby the enfolding leafsheaths as to be inaccessi-ble to them. Thus it isthat the stage of advance-ment in the growth of thewheat stem at the time ofoviposition of the summergeneration of femalesdetermines whether thelarvte will he well upwardin the straw, and there-fore removed after har-vest, or lower down andconsequently left in thefiekl in the stubble. The method of ovi-position and the pointwhere the egg is usuallyformed is shown in The larva forms nogall, nor does it hardenthe stem within which itdevelops. There is nor-mally but
Insect pests of farm, garden and orchard . so coveredby the enfolding leafsheaths as to be inaccessi-ble to them. Thus it isthat the stage of advance-ment in the growth of thewheat stem at the time ofoviposition of the summergeneration of femalesdetermines whether thelarvte will he well upwardin the straw, and there-fore removed after har-vest, or lower down andconsequently left in thefiekl in the stubble. The method of ovi-position and the pointwhere the egg is usuallyformed is shown in The larva forms nogall, nor does it hardenthe stem within which itdevelops. There is nor-mally but one larva in each joint; but if several eggs have beenplaced between joints and produce larvse there will be one in thecentre of the stem just above the joint and others in the walls justunder the internal wall-covering or inner epidermis. These larvaein the walls of the straws do not, as a rule, kill the stem, buttheir effect is to curtail the yield by reducing the weight. Thelarvse develop rapidly and reach their full growth before the. Fig. 103.—Wheat straw-worm, showingpoint wliere female of the spring formdeposits the egg in yomig wheat in earlyspring. Enlarged showing position of eggat right. (After Wester, U. S. Dept. Agr.) 142 INSECT PESTS OF FARM, GARDEN AND ORCHARD straw has hardened. By October, in the Middle West, thoughearlier in the South, they pass into the pupal stage, in which, as arule, they remain until early spring, whereupon they develop toadults and gnaw their way out. In the Northwest, where bothwinter and spring wheat are grown, the injury is particularlysevere to spring wheat, as the adults of the second generation fromvvinter wheat oviposit upon it while it is still young and ruin it inmuch the same way as the first generation does on the winterwheat in spring. Volunteer plants which carry the pest overwinter have the same effect in increasing the injury to springwheat. Control.—-A rotation of crops which will eliminate the growingof wheat two yea
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