2 BULLETIN 1066, IT. S. DEPARTMENT OE AGRICULTURE. 



THE BUTTERNUT CURCULIO. 1 



The butternut curculio has been known commonly in the past 

 either as the " walnut weevil " or " walnut curculio." It would seem 

 that for the members of this group whose larvae feed in immature 

 nuts the term " curculio " is to be preferred in order to disassociate 

 them in the popular mind from members of the Balaninus group, 

 which have long been known as "nut weevils." The other part of the 

 name is here restricted to " butternut " for the reason that this species 

 appears to confine its attacks almost exclusively to our native butter- 

 nut (Juglans cinerea) and to introduced walnuts of the butternut 

 type. There is a very similar but distinct species to which the name 

 " walnut curculio " could be applied with equal appropriateness. In 

 rearing several hundred specimens the writer has failed to obtain 

 a single individual of G. juglandis from infested young black wal- 

 nuts {Juglans nigra), the species commonly attacking black walnuts 

 being C onotrachelus retentus Say, described on pages 7-11. One 

 beetle of C. retentus was found among a lot of beetles of C. juglandis 

 reared from butternuts, and it is possible that with both species of 

 insect there is occasional interchange of hosts. 



The butternut curculio also attacks and injures seriously the fruit 

 and small branches of various species of introduced walnuts, being 

 especially destructive to the Japanese walnuts (/. sieholdiana and 

 J . cordiformis) which are of the butternut type. (PI. II, D; PL 

 III, B.) 



DISTRIBUTION. 



The known range of the butternut curculio extends from the 

 Provinces of Ontario and Quebec, Canada, south through the New 

 England States, Wisconsin, Iowa, and Kansas to Alabama and 

 Georgia. Britton and Kirk 2 record it from 20 States within the 

 boundary just given. The distribution of the insect follows rather 

 closely the natural range of the butternut, which is its favorite native 

 food plant. Throughout the general range of the insect there are 

 evidently many localities, even where host trees abound, in which it 

 is ver}^ rarely found. In many other localities it is abundant and 

 destructive. 



FOOD PLANTS. 



Britton and Kirk - give the food plants in the order of preference 

 shown as follows : Juglans cordiformis, J. sieholdiana, J. cinerea, J. 

 regia, J. nigra, and J. mandshwia. They quote Dr. Eobert T. Mor- 



1 Conotrachelus juglandis Lee. ; suborder Rhynehophora, family Curculionidae, tribe 

 Cryptorhynchini. 



2 Britton, W. E., and Kirk, H. B. Life history and habits of the walnut weevil 

 or curculio. In 12th Ann. Rept. State Ent. Conn., p. 240-253. 1912. 



