. The butterfly book; a popular guide to a knowledge of the butterflies of North America. Butterflies. Fig. 9. —Upper end of egg of Pieris oleracea, greatly magnified, show- ing the micropyle. Fig. 10.—Egg? oiGrapta conu ma, laid in string-like clus- ters on the under side of leaf. (Magni- fied.) pillar, after it is hatched, is destined to live, and the female re- veals wonderful instinct in selecting plants which are appropriate to the develop- ment of the larva. As a rule, the larvse are restricted in the range of their food-plants to certain genera, or families of plants. The eggs are depos
. The butterfly book; a popular guide to a knowledge of the butterflies of North America. Butterflies. Fig. 9. —Upper end of egg of Pieris oleracea, greatly magnified, show- ing the micropyle. Fig. 10.—Egg? oiGrapta conu ma, laid in string-like clus- ters on the under side of leaf. (Magni- fied.) pillar, after it is hatched, is destined to live, and the female re- veals wonderful instinct in selecting plants which are appropriate to the develop- ment of the larva. As a rule, the larvse are restricted in the range of their food-plants to certain genera, or families of plants. The eggs are deposited sometimes singly, sometimes in small clusters, sometimes in a mass. Fertile eggs, a few days after they have been deposited, frequently undergo a change of color, and it is often possible with a magnifying-glass to see through the thin shell the form of the minute caterpillar which is being developed within the egg. Unfruitful eggs gen- erally shrivel and dry up afterthe lapse of a short time. The period of time requisite for the development of the embryo in the egg varies. Many butterflies are single-brooded; others produce two orthree gen- erations during the summer in temperate climates, and even more generations in subtropical or tropical climates. In such cases an interval of only a few days, or weeks at the most, separates the time when the egg was deposited and the time when the larva is hatched. When the period of hatching, or emer- gence, has arrived, the little caterpillar cuts its way forth from the egg through an opening made either at the side or on the top. Many species have eggs which appear to be provided with a lid, a portion of the shell being separated from the re- mainder by a thin section, which, when the caterpillar has reached the full limit allowed by the egg, breaks under the pressure of the enlar- ging embryo within, one portion of the egg flying off, the remainder adhering to the leaf or twig upon which it has been —Eggs
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbutterf, bookyear1904
