Elementary principles of agriculture Elementary principles of agriculture : a text book for the common schools . elementaryprinci02ferg Year: 1913 1G2 Elewentary Principles of Agriculture other groups of insects by the way they get their food from the plant or animal. Instead of having jaws with which they may bite off and chew their food, their mouth parts are shaped into a kind of tube which they use to suck blood or sap, nectar or viscid matter. The squash-bug (Fig. 99) and the chinch-bug get their food by sucking. Plant lice, such as the green bug, and San Jose scale (Fig. 100) are also
Elementary principles of agriculture Elementary principles of agriculture : a text book for the common schools . elementaryprinci02ferg Year: 1913 1G2 Elewentary Principles of Agriculture other groups of insects by the way they get their food from the plant or animal. Instead of having jaws with which they may bite off and chew their food, their mouth parts are shaped into a kind of tube which they use to suck blood or sap, nectar or viscid matter. The squash-bug (Fig. 99) and the chinch-bug get their food by sucking. Plant lice, such as the green bug, and San Jose scale (Fig. 100) are also sucking insects. ' ,. __| i^ ^ ^ â ;_ 1 lu; lUU .^Jii Jose scale on plum. .4, natural size; 6, luaijuitieci c, greatly magnified. Insects should not be classed as 'biting insects' and 'sucking insects' because some species have biting mouth parts at one stage of their life cycle and sucking mouth parts at another. The caterpillars gnaw or bite their food, while the parent moths or butterflies have a sucking tongue. Some kinds with sucking mouth parts are comparatively free, their host and habitat being often unknown. Many kinds, however, have developed fixed parasitic habits. Most of the bloodthirsty pests belong here, such as horse and cattle flies, the mosquitos and the common bed-bug. The sucking insects are usu- ally external feeders. Exceptions are noted in the case of the horse bot and the cattle warble. 230a. Structure of Insects. For this exercise the pupil should secure good specimens of the grasshopper and butterfly, as these
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