Economic entomology for the farmer and fruit-grower [microform] : and for use as a text-book in agricultural schools and colleges economicentomolo00insmit Year: 1896 iS ylA' ECONOMIC ENTOMOLOGY. a rule, they will bear close watching. One thing is certain, how- ever : no insect with this type of mouth structure can be reached by means of a stomach poison. Destruction through its food is, therefore, absolutely impossi- ble, because we cannot poison the plant juices by any method thus far at our command. An insect of this kind is incapable of eating any solid food what- ever, and no matter how
Economic entomology for the farmer and fruit-grower [microform] : and for use as a text-book in agricultural schools and colleges economicentomolo00insmit Year: 1896 iS ylA' ECONOMIC ENTOMOLOGY. a rule, they will bear close watching. One thing is certain, how- ever : no insect with this type of mouth structure can be reached by means of a stomach poison. Destruction through its food is, therefore, absolutely impossi- ble, because we cannot poison the plant juices by any method thus far at our command. An insect of this kind is incapable of eating any solid food what- ever, and no matter how thor- oughly covered with a corro- sive poison the outside of our plants may be, it would get none, since it only punctures the tissue without absorbing any portion of the outer sur- face. Thus the determination of the type of mouth structure often limits or decides the char- acter of the remedy to be used in destroying the insect. Among the Diptera, or flies, we have a number of interest- Mouth parts of a plaiit-louse.—a, the ing modifications of the suck- jointed beak; (?, the lancets, much enlarged; Jj^^r niOUth. One SCricS is fur- c and rf illustrate the feeler and foot. .*,,.', . . ' nished with lancets similar to those in the bugs, but more numerous, representing different mouth structures, and not always carried into the head itself The sucking structure is also quite different, and never forms a rigid, jointed beak. Mosquitoes and horse-flies are examples of this kind ; but gradually the lancets disappear, and in most of the flies only the sucking lip, often greatly and interestingly developed, remains. The common house-flies and blow-flies are types of this modified form, and are capable of taking liquid food only, though often seen attacking solids. If the mouth of a fly be examined under the microscope, there will be seen at the tip of the lip a series of deep grooves, stiffened with chitinous loops, and armed with sharp projecting edges. When the fly wishes to fee
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