The Life-History and Anatomy of Butterflies 



within comparatively recent years been discovered in connection 

 with the larval stage of certain small butterflies belonging to 

 the family Lye ami dee. The caterpillars are carnivorous, or rather 

 aphidivorous; they live upon aphids, or plant-lice, and scale- 

 insects, and cover 

 themselves with the 

 white exudations or 

 mealy secretions of 

 the latter. This trait 

 is characteristic of 

 only one of our North 

 American species, the 

 Harvester (Feniseca 

 tar qn milts). 



In addition to 

 being protected from 

 enemies by having 

 colors which enable 

 them to elude obser- 

 vation, as has been 

 already stated, some 

 caterpillars are pro- 

 vided with other 



means of defense. FIG. 21. Early stages of the goatweed butterfly: , 



T , -,, f ,, caterpillar; b, chrysalis; c. leaf drawn together at edges 



The caterpillars of the to form a nek (Natural size.) (Riley.) 



swallowtail butter- 

 flies are provided with a bifurcate or forked organ, generally 

 yellow in color, which is protruded from an opening in the skin 

 back of the head, and which emits a powerful 

 odor (Fig. 22) , This protrusive organ evidently 

 exists only for purposes of defense, and the secre- 

 tion of the odor is analogous to the secretion 

 of evil odors by some of the vertebrate ani- 

 mals, as the skunk. The majority of caterpil- 

 lars, when attacked by insect or other enemies, 

 defend themselves by quickly hurling the an- 

 terior part of the body from side to side. 

 Moults. Caterpillars in the process of growth and develop- 

 ment from time to time shed their skins. This process is called 

 moulting. Moulting takes place, as a rule, at regular intervals, 



Q 



FIG. 22. Head 

 of caterpillar of Pa- 

 pilio troilus, with 

 scent-organs, or os- 

 materia, protruded. 



