The Life-History and Anatomy of Butterflies 



Fig. 9. — Upper end of 

 egg of Pieris oleracea, 

 greatly magnified, show- 

 ing the micropyle. 



Fig. 10. — Egg? 

 oiGrapta com- 

 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 larvae 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 after the lapse of ashorttime. 

 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 deposited. 



Fig. 1 1.— Eggs 

 of Vanessa an- 

 tiopa, laid in a 

 mass on a twig. 



CATERPILLARS 



Structure, Form, Color, etc.— The second stage in which the 

 insects we are studying exist is known as the larval stage. The 

 insect is known as a larva, or a caterpillar. In general cater- 



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