THE PHYLA ARTHROPODA AND ONYCHOPHORA 



hind wings. Eggs of the potato beetle are fastened to leaves of the potato 

 plant; at the close of the embryonic period the humpbacked larvae, or grubs, 

 emerge and begin their depredations by feeding on the vines. After a suc- 

 cession of larval stages, the mature grub crawls down from the plant and 

 burrows into the soil before transforming into a pupa. The adult emerges 

 after a week or 10 days and resumes the feeding interrupted by the pupal 

 stage. The history of the potato beetle is interesting; the insect is native 

 to western North America, where in its natural state it feeds upon purple 

 nightshade, a wild species related to the potato. When potato culture was in- 

 troduced into the Western states, the beetle transferred its activities to the 

 potato plant and has since spread widely, by natural means, to practically 

 every country where the potato is grown. Reservoir populations of potato 

 beetles may always be found in stands of purple nightshade. 



Fig. 15.31. Lepidoptera. 

 Caterpillars usually possess 

 mandibulate mouth parts like 

 those of the moth larva shown 

 in .4. With metamorphosis, 

 the mouth parts change to a 

 suctorial type like those of the 

 butterfly in B. This involves 

 extreme modification of the 

 maxillae in particular, which 

 become lateral halves of a 

 long tube, coiled at rest but 

 capable of unrolling to reach 

 the nectar in deep flowers. 

 {A, photograph by Charles 

 Walcott; B, photograph by 

 E. S. Ross.) 



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