The Life-History and Anatomy of Butterflies 



FIG. 9. Upper end of 

 egg of Pieris oleracea, 

 greatly magnified, show- 

 ing the micropyle. 



FIG. i o. Eggs 

 ofGrapta 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 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 or three 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 

 atthesideoronthetop. Many species have eggs which appearto 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. ii. 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- 



