Entomology : with special reference to its biological and economic aspects . Eggs of various insects. A, butterfly, Polygoiiia interrogationis; B, house fly,Musca domestica; C, chalcid, Bruchophagus funebris; D, butterfly, Papilio troilus; E,midge, Cecidomyia trifolii; F, hemipteron, Triphlcps insidiosiis; G, hemipteron,Podisus spinosus; H, fly, Drosophila ampelophila. Greatly magnified. i6o ENTOMOLOGY quite fantastic. Something of the variety of form is shownin Fig. 207. As regards size, most insect eggs can be distinguished by thenaked eye; many ofthem tax the vision,however, for example,the
Entomology : with special reference to its biological and economic aspects . Eggs of various insects. A, butterfly, Polygoiiia interrogationis; B, house fly,Musca domestica; C, chalcid, Bruchophagus funebris; D, butterfly, Papilio troilus; E,midge, Cecidomyia trifolii; F, hemipteron, Triphlcps insidiosiis; G, hemipteron,Podisus spinosus; H, fly, Drosophila ampelophila. Greatly magnified. i6o ENTOMOLOGY quite fantastic. Something of the variety of form is shownin Fig. 207. As regards size, most insect eggs can be distinguished by thenaked eye; many ofthem tax the vision,however, for example,the elhptical eggs ofCccidoiiiyia Icguiiiiiii-cola. which are mm. in length. Three eggs of the cabbage butterfly, Pierisraf>/r. Greatly magnified, but all drawn to samescale. and .0 / n mm. ni Fig. 209. width; the oval eggsof the cccropia moth,on the other hand, are as long as 3 mm. The egg-shell, or chorion, secretedaround the ovum by cells of the ovarianfollicle, may be smooth but is usuallysculptured, frequently with ridgeswhich, as in lepidopterous eggs, mayserve to strengthen the shell. Theornamentation of the egg-shell is oftenexquisitely beautiful, though the par-ticular patterns displayed are probablyof no use, being incidentally producedas impressions from the cells whichsecrete the chorion. Variations ofform, size and pattern are frequent ineggs of the same species, as appears inFig. 208. Always the chorion is penetrated byone or more openings, constituting themicropylc. for the entrance of sperma-tozoa. As a rule, the eggs when laid are accompanied by a fluid ofsome sort, which is secreted usually by a cement gland orglands, opening into the vagi
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectentomology, bookyear1
