498 



while others contain none at all. 



In general Brnchids which breed in starchy seeds cannot 

 breed in those withont starch and vice versa. The soy bean in 

 which the carbohydrate is rednced and not in the form of 

 starch, however, serves for the development of Bruclius chinen- 

 sis, B. qua.dnmacidat}is, the dolichos weevil, and Zahrotes, 

 species ordinarily breeding in the other starchy food legumes. 

 Its carbohydrate is, however, of a form similar to starch and 

 is present to about .12 of the dry weight of the seed. 



In general the food legumes contain but little oil while in 

 the peanut it may be present to .SS-.IH of the weight of oil, 

 largely replacing the starch. While the eggs of B. chinensis, 

 B. quadrimaculatusy the dolichos weevil, and Zahrotes are 

 readily laid upon peanuts from which the shells have been re- 

 moved and their larvae enter the cotyledons and the larvae 

 of B. oMectiis will, likewise, enter them, none of these species 

 can develop and I have supposed their death to be due to the 

 oil. I was, therefore, greatly surprised to find B. pruiiiiiius, 

 under similar conditions, was able to breed in peanuts, al- 

 though its other host seeds contain no starch and but little oil. 



Many legumes contain poisonous i)rineiples, particularly 

 alkaloids and glucosides, and we should expect Brnchids to be 

 affected by some of these. Probably the inability of Caryoho- 

 rus gonagra to breed in the seeds of Ahrus precatoriiis, and 

 Pithecolobinni dulce, upon which it oviposits, and into which 

 the larva can penetrate, is due to poisonous principles in them. 



Some seeds are so small as to prevent the oviposition of Bru- 

 chidae on their surface, since the insect would not be able to 

 reach conveniently any part of the surface of the seed with its 

 ovipositor while resting on its surface and the weight of the 

 insect also tends to dislodge the seed and its precarious position 

 on a small seed seem to disturb the Bruchid so as to prevent 

 egg-laying. Thus Bruchus pruininus, which is very catholic in 

 its taste in regard to oviposition, is usually unable to deposit its 

 eggs on such small seeds as those of Indigifera anil, Desmo- 

 dium uncinatum, the smaller-seeded Cratalarias, Ph<iseolus 



