494 



bananas. What we slionld need to suppose is a variation in its 

 powers of utilizing food and we do not know liow little or how 

 great a departure from the normal this would require, nor if 

 it would have to be variation in the structure of the larval 

 mouth parts or of its alimentary canal, or in the composition 

 of its digestive fluids, or in its nervous control, or all these 

 combined. We have found the Bruchus pnriiiinus ovipositing on 

 the seeds of Ipomoea and here again to secure the development 

 of the habits of such species as the North American B. dis- 

 coideus or the South African B. convolvuli breeding in convol- 

 vulaceous seeds it is only variation in the powers of food utili- 

 zation which would be needed. Perhaps the same is true of 

 the ISTorth American species B. flavicornis and B. hibisci 

 breeding in the seeds of malvaceous plants and B. alhoscutel- 

 latus in the capsules of Ludwigia. In the European B. margi- 

 nelliis such variation has, perhaps, been observed or at least it 

 has an unusual variability in the utilization of food ; for while 

 it seems ordinarily to breed in the pods of the legume, Oxytro- 

 pis gJycophyJlos it has been observed breeding in the capsules 

 of Yerbascum officinale widely separated in botanical relation- 

 ship and in other ways. 



In considering evolutionary matters too often attention has 

 been centered upon obvious structures, especially those used 

 for the distinction of species in systemic botany and zoology. 

 Food habits, reflexes, tropisms, and transformations are no 

 less characters of species and have played a large part in the 

 development of the species and require consideration when we 

 are making out our explanations. 



Leguminous Pods and Seeds with Reference to Their 

 Infestation by Bruchidae. 



The Bruchidae were without doubt descended from a Chry- 

 somelid group in which the larvae attacked the green pods of 

 legiunes and the oviposition of such species as Bruchus ohtectus 

 in which the eggs are laid in crevices in the pods of the host 

 plant may perhaps represent the primitive method of egglaying 



