496 



there are other mechanical difficulties iu the way of a Bruchid 

 larva penetrating this seed. We may conceive of a Bruchid 

 larva overcoming such a difficulty as this, however, and that 

 presented by similar difficulties in the hardness of seed coats 

 and tough albumen by timing its attempt at entering so that it 

 would have to encounter them in an immature condition before 

 they have hardened. Whether to serve such a purpose or not, 

 though probably for some other reason, the pea bruchus ovi- 

 posits only upon the green pods of its host plants. J^ow in the 

 Islands the host plants of this Bruchus are but rarely cultivated 

 and if the species should be brought in through the importation 

 of peas, as we know has been frequently, it would rarely be 

 able to find conditions under which it could breed. This seems 

 to me the probable reason that this species has not as yet been 

 able to establish itself in the Islands. 



In the case of Cassia grandis there is within the pod in the 

 little compartment about each seed a considerable amount of 

 a pitchy material surrounding the seed which would serve to- 

 retard a Bruchid larva and, perhaps, to cause its death. A 

 similar substance but much less copious in quantity is found 

 in the pods of Cassia fistula but it does not in either case 

 wholly serve to prevent the entrance of the Caryohorus larva. 



On the outer surface of the seeds of Bauhinia tomentosa 

 and Bauhinia monandra is a layer of material which swells 

 up with moisture and shreds away and would serve to detach 

 any bruchus egg attached to it. This does not serve to prevent 

 the entrance of the Caryohorus larva since the eggs of that 

 species are usually attached to the pod and the entrance of 

 the larva is affected before the pod is opened and the seed 

 exposed to moisture. Eggs of Bruchus pruininus deposited on 

 these seeds in captivity were detached when added moisture 

 caused the swelling and shredding away of this layer. 



The surface of some seeds such as those of different species 

 of Crotalaria seem to be of such a nature as to prevent the 

 attachment of bruchus eggs. It may be, however, that there 

 is some other reason such as odor or size which prevented ovi~ 



