498 



while others contain none at all. 



In general Bruchids which breed in starchy seeds cannot 

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

 which the carbohydrate is reduced and not in the form of 

 starch, however, serves for the development of B melius chinen- 

 sis, B. quadrimaculatus, the dolichos weevil, and Zabrotes, 

 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 ,28-45 of the weight of oil, 

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

 B. quadrimaculaiusy the dolichos weevil, and Zabrotes are 

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

 moved and their larvae enter the cotyledons and the larvae 

 of B. obtectus 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. pniiiiimis, 

 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 principles, particularly 

 alkaloids and glucosides, and we should expect Bruchids to be 

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

 rus gonagra to breed in the seeds of Abrus precatoiius, and 

 Pithecolobium clulce, 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 Bm- 

 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 Bru<;hid 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 uncinatwm, the smaller-seeded Crotalarias, Ph<iseolus 



