. Manuel de légume-insectes de jardin. d constituent la dernière genres-tion de la saison. À partir de onze-totwenty producedannually sont deux générations, chaque femelle donnant naissance tonearly cinquante jeunes. Avec l'avènement ofcool aptères, météo ponte des femalesand ou sans ailes, ailes, malesare rarement produite. Les petits œufs noirs aredeposited sous terre dans les galeries de fourmis où ils sont soignés pour tillthe au printemps suivant. La femme grownviviparous (Fig. Ysinch 137) est d'environ de long, vert bleuâtre, dépoussiéré avec un waxypulverulence blanchâtre. La tête et les bandes transversales sur le thoraxare b

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. Manual of vegetable-garden insects. d constitute the last genera-tion of the season. From eleven totwenty-two generations are producedannually, each female giving birth tonearly fifty young. With the advent ofcool weather, wingless egg-laying femalesand wingless, or rarely winged, malesare produced. The small black eggs aredeposited underground in the galleries ofthe ants where they are cared for tillthe following spring. The full-grownviviparous female (Fig. 137) is about ysinch in length, bluish green, dusted with a whitish waxypulverulence. The head and transverse bands on the thoraxare black. In the winged form, the head and thorax areblack or dark brown and the abdomen is pale green withthree distinct blackspots on each side(Fig. 138). _ By the time thecorn is planted andcomes up, theaphids have becomecrowded on theroots of the weedsand many wingedforms have devel-oped. At this timethe weed roots havebecome hardened and are thus less favorable for the develop-ment of the lice. The ants transfer many of the wingless. Fig. 138. Winged viviparous female corn-rootaphis (X 16). CORN INSECTS 221 aphids from the weeds to the corn roots and also seize any ofthe winged migrating forms that come their way and carrythem down to the roots. In this way the corn soon becomesbadly infested. The injury is ordinarily first noticed in irregularpatches usually on the lower ground. The loss of sap causedby the feeding of the aphids lessens the vitality of the plant, causing the leaves to turn yellowish or reddish. The aphis ismost destructive in years of drought because under such condi-tions the plants are least able to bear the loss of sap. Cornplants badly stinited by the root-aphis often fail to bear earsor produce only nubbins. Control. Experiments and the experience of practical corn-growers inIllinois have shown that the losses caused by the corn root-aphis may be in large measure prevented by plowing landintended for corn to a depth of six or seven inches early in thespri

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