Economic entomology for the farmer and fruit-grower : and for use as a text-book in agricultural schools and colleges . y,the supply of sap is not so plenty, and these features becomemore marked through the autumn months until, with the ap-proach of cold weather, plant growth entirely ceases. It becomesnecessary now to provide for the continuation of the speciesduring winter, and sexed forms are developed. The males areusually winged and appear a short time before the females, which THE INSECT WORLD. 125 differ by the lack of wings and the usually small size comparedwith the normal sexless for
Economic entomology for the farmer and fruit-grower : and for use as a text-book in agricultural schools and colleges . y,the supply of sap is not so plenty, and these features becomemore marked through the autumn months until, with the ap-proach of cold weather, plant growth entirely ceases. It becomesnecessary now to provide for the continuation of the speciesduring winter, and sexed forms are developed. The males areusually winged and appear a short time before the females, which THE INSECT WORLD. 125 differ by the lack of wings and the usually small size comparedwith the normal sexless form. Pairing takes place as soon asthe female is sexually mature, and in a very few days after-wards eggs are laid. In many instances the ^^<g supply isexceedingly small, indeed there may be one only matured bya female. Even this may remain within the body of the parent,who simply dries up, the skin shrivelling around and form-ing a protection to the ovum. More usually several eggs areproduced, and these of large size in proportion to the size ofthe insect that lays them. They are green or greenish-brown Fig. Hop-louse, male; return migrant. in color when laid, sometimes yellowish, and frequently darkento black. They are placed in sheltered situations on plants, and,in the caseof orchard trees, are usually found at the tips of twigs,around the buds, or on the leaf-scales, where vegetation will firststart in the spring following. They are very firm in texture andvery resistant to insecticides ; in fact, it is impossible to destroythem except by the most caustic mixtures. It has been alreadyindicated that there are many exceptions to this general life his-tory, and one kind of exception we find where species feed dur- 126 AN ECONOMIC ENTOMOLOGY. ing the summer upon a plant which dies down to the ground,leaving nothing through the winter. In such cases there is analternate food-plant, upon which the winter and early spring arepassed. From this the insects migrate in early su
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