. Entomology : with special reference to its biological and economic aspects. asily introducedinto the stio^niatic cJiaiiibcr of a new flower visited by the in- ^^ ^^ sect. Then the struggles ofthe insect ordinarily break thestem, or retiiiaciihiiii, of thepollinium and free the , however, the insect losesa leg or else is permanentlyentrapped, particularly in thecase of such large-floweredmilkweeds as Asclepias cor nut i,which often captures bees, fliesand moths of considerable is accomplished bya great variety of insects, chiefly Hymenoptera, Diptera, Lepi-doptera


. Entomology : with special reference to its biological and economic aspects. asily introducedinto the stio^niatic cJiaiiibcr of a new flower visited by the in- ^^ ^^ sect. Then the struggles ofthe insect ordinarily break thestem, or retiiiaciihiiii, of thepollinium and free the , however, the insect losesa leg or else is permanentlyentrapped, particularly in thecase of such large-floweredmilkweeds as Asclepias cor nut i,which often captures bees, fliesand moths of considerable is accomplished bya great variety of insects, chiefly Hymenoptera, Diptera, Lepi-doptera and Coleoptera. These insects when collected aboutmilkweed flowers usually display the pollinia dangling fromtheir legs, as in Fig. 255. The details of pollination may be gathered by a close ob-server from observations in the field and may be demonstratedto perfection by using- a detached leg of an insect and draggingit upward between two of the hoods of a flower; first to re-move the pair of pollinia and then again to introduce one ofthem into an empty stigmatic A wasp, Sphex ichncumonea, with pol-linia of milkweed attached to its enlarged. 264 ENTOMOLOGY Fig. 256. Yucca.—An extraordinary example of the interdependenceof plants and insects was made known by Riley, whosedetailed account is here summarized. The yuccas of thesouthern United States and Mexico are among the few plantsthat depend for pollination each upon a single species of pollen of Yucca filarncntosa cannot be introduced into thestigmatic tube of the flower without the help of a little whitetineid moth, Pronuba yuccasella, the female of which pollen-izes the flower and lays eggs among the ovules, that her larvae may feed upon theyoung seeds. Whilethe male has no un-usual structural pecu-liarities, the female isadapted for her specialwork by modificationswhich are u n i q u ea m o n g Lepidoptera,namely, a pair of pre-hensile and spinousmaxillary tentacles (Fig. 256, A) and al


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Keywords: ., bookcentury1900, bookdecade1900, booksubjectentomology, bookyear1