ACTING STATE ENTOMOLOGIST. 
65 
Peaches, our Cherries and our Apricots, such a phenomenon has as yet occurred, and 
that the plum-feeding form is a different species from the cherry-feeding form, and that 
again from the peach-feeding form, and so on. There is no reason whatever to think 
so. But there actually,’in my opinion, does exist a “ Phytophagic species” of the 
common Curculio, which is uniformly one half larger and which in the larva state feeds, 
not upon stone-fruit or pip-fruit, but upon green Butternuts and Walnuts {,Juglans ,) 
from the former of which I bred two individuals Aug. 13tli. Of this peculiar type of 
Curculio I sent specimens 6 years ago to our great North American authority in the 
Order of Beetles, Dr. J. L. LeConte ; and he pronounced them to be mere varieties of 
the Plum Curculio. They scarcely differ from that insect in any other perfectly constant 
character than size ;* and at first sight we might suppose, that the increased size was 
caused merely by the Butternuts and Walnuts being more nourishing and stimulating 
food than Plums and Peaches ; and that a Curculio bred in a Butternut would be just 
as likely as not to lay its eggs in a Plum, and the reverse ; thus showing that here no 
distinct “Phytophagic species” has yet been formed. This was the opinion of Dr. 
Fitch ; for he says that “ the specimens found on Butternut trees are always larger 
in size than those found on cultivated fruit-trees, indicating that they have been 
better fed during the larva or growing period of their lives.” {Address on Curculio , 1860, 
p. 17.) But there is a remarkable fact, which proves satisfactorily to my mind that this 
cannot be so, and that the two races are perfectly distinct and do not interbreed, each 
confining itself strictly to its peculiar food-plants. The fact is simply this : —I have 
beaten hundreds and hundreds of Curculios of the small-sized type off fruiting wild Plum- 
trees, but I never yet beat a single specimen of the large-sized type, which inhabits 
Butternuts and Walnuts, off a Plum-tree of any species or in any state. Of course, if 
that large-sized type had acquired no hereditary indisposition or incapacity to breed in 
Plums, it would be just as likely to occur on the Plum as on the Butternut or Walnut. 
But if, as the facts indicate, it really has acquired such a hereditary indisposition or 
incapacity, and if it interbreeds only with its own race, then —according to what I con¬ 
sider to be the essence of the term “ species” — it is a distinct species. You may, if you 
please, for the sake of precision, give it a distinctive appellation, and call it, for 
example, a “ Phytophagic species ;” but still it is, in my acceptation of the term, a true 
species. 
In the recent much enlarged and improved edition of the “Origin of Species,” Mr. 
Darwin has quoted with general approbation my views upon this very interesting sub¬ 
ject, but has incidentally remarked that lam “ forced to assume that those forms which 
have lost the capacity for intercrossing should be called species.” {Fourth English 
edition , pp. 55-6.) This, I think, can scarcely be called an assumption. It is a definition. 
* There is, I believe, a slight, but perfectly constant colorational character by which these two forms 
are distinguishable. The broad band behind the polished black humps on the wing-cases is, in the 
large-sized nut-inhabiting form, of a dingy white color with a few milk-white spots. In the small plum- 
inhabiting form, this same band is of a bright ochre-yellow color, with more or less milk-wlute spots, 
which last however, never occupy more than one-half of the ochre-yellow band. Moreover, I am informed 
by Dr. Hull, that the larva of the large-sized form — with which he has long been familliar —occurs 
with him in hickory-nuts having their shucks marked by the characteristic crescent-slit, and that this 
larva “penetrates to the kernel of the nut.” Whereas, as is well known, the larva of the small sized 
form that frequents the plum, never under any circumstances penetrates to the kernel of that fruit. 
This difference in the habits of the two forms, is certainly very remarkable. 
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