85 



INSECTS INFESTING THE PLUM.— On the Fruit. 

 CHAPTER XI. — The Plum Curculio. (Conotrachelus nenuphar, Herbst.) 



In the Practical Entornologist (Vol. II. pp. 75 — 79)1 have dilated 

 so fully on the Natural History of this pestilent' little Snout-beetle, 

 and on the most approved methods of fighting it, that it will only be 

 necessary to add a few items here on these two subjects, and to cor- 

 rect such errors as I have fallen into. 



Although the Curculio now infests the cultivated species of Plum 

 (Prunus domestica, Linnaeus,) to fully as great an extent as our com- 

 mon wild species (Primus americana,) yet it is only at a compara- 

 tively recent date that it attacked our cultivated Plums, and since 

 that epoch it has been growing every year worse and worse, and 

 making onslaughts upon other fruits such as the Peach, the Cherry, 

 'and even the Apple. "Curculios," said the Hon. D. J. Baker, in 

 1855, "were unknown and never made their incursion into this re- 

 gion, until some years after the organization of our State Govern- 

 ment," A. D. 1818. {Transactions Illinois State Agricultural So- 

 ciety, II. p. 48.) There can be little doubt, however, that Curculios 

 have existed for time immemorial in our State, breeding in wild 

 opiums; because, before tame plums and peaches and apricots were 

 imported into this coimtry from Europe, the insect must necessarily 

 have bred in the wild plum, and wild plums are very abundant in 

 Illinois, and moreover we know, from our present experience, that the 

 climate of Illinois is quite congenial to the constitution of this insect. 

 It would certainly, therefore, seem to follow that, in this as in so 

 many other cases, when an insect has incidentally acquired a habit of 

 feeding indiscriminately upon a different species of plants, to that 

 upon which alone it naturally fed in the first instance, it transmits 

 that habit by the laws of inheritance to its immediate descendants. 

 When a race has once been formed, having such a habit, nothing seems 

 more natural than that, under certain peculiar circumstances, such 

 for instance as the absence of the original food-plant, another race 

 should be very slowly and gradually formed, which exclusively attacks 

 the new food-plant. If we suppose this second race to interbreed ex- 

 clusively with itself, and to have thereby acquired, in a long series of 

 ages, either a moral indisposition or a physical incapacity to interbreed 

 with individuals belonging to the original race, then it becomes almost 

 as effectually isolated from the original race, as if it were separated 

 therefrom by the Atlantic Ocean, or by such an insurmountable bar- 

 rier as the Rocky Mountains. Now, we know that races of insects, 

 and indeed of other animals as well, when separated from each other 



