495 



from which later forms developed in which the eggs were 

 cemented to the larval food. There can be l)iit little doubt 

 that the evolution of the Bruchidae has proceeded in directions 

 limited by the peculiarities of the Leguminosae and there is an 

 interesting field for work in the investigation of the factors 

 which limit the attacks of the different species of Bruchidae. 

 In some experiments summarized further on I have attempted 

 to make a beginning on such investigation. Some of these 

 factors are readily discerned while others remain elusive. The 

 following notes and inferences in regard to the limitation of 

 Bruchid attacks have seemed worth recording. 



When a species of Bruchidae oviposits in crevices in the 

 pods or in openings made by the female into the pod or if the 

 eggs are cemented to the seed but not to the pod the structure 

 of the pod and its behavior upon ripening are important factors 

 in reference to Bruchid injury. Thus Prosopis juViflora is not 

 naturally attacked by BrucJius pridninus because of its inde- 

 hiscent pods yet it readily breeds in the seeds when the cover- 

 ings are artificially removed and this is also true of the peanut 

 and the beggar's tick (Desmodium uncinatum). 



In the species of Bruchidae cementing their eggs to the 

 larval food they may be attached either to the pods or to the 

 seeds, or in many species either to the pods or to the seeds. 



Bruchus pisorum apparently always oviposits upon the 

 pods; Bruchus pruininus apparently always upon the seed; 

 while the dolichos bruchus, Bruchus chinensis, and Caryohorus 

 gonagra may place their eggs either upon the seeds or the pods 

 of their host plants. In any case the larva of the Bruchid 

 finds confronting it on hatching the work of penetrating into 

 the cotyledons of the seed which forms its principal or perhaps 

 its exclusive food. If the egg should have been placed upon 

 a dry, hard, woody pod such as that of Delonix regia we may 

 suppose such a barrier might serve to exhaust the reserve 

 energy of the larva so that it would perish before it could 

 have opportunity for feeding. I have no record of finding 

 the seeds of this species attacked by Caryohorus goruigra but 



