Although the resulting brood generally proves more destructive in the mountain regions than the incoming storm, yet this does not appear so far to have been the case in the Mississippi Valley; and as a preventive or remedy for the original hordes dispenses with the necessity of battling with their progeny, it is against these the general government should direct its efforts in an earnest and determined manner. From what is known of the habits of this species we may be assured that it will never become a permanent resident of the Mississippi Valley, as its sudden transfer from the dry and rarified air of the elevated mountain regions to the heavy and moist atmosphere of the States requires too rapid a change in its nature for it to undergo. But, sup. posing it should become habituated to this region and overcome all climatic difficulties, it is very probable, in fact I might say almost cer. tain, that it would lose its migratory disposition, and if but a variety of C. femur-rubrum, as I strongly suspect, would in all probability revert to that form. The origin of the migratory habit of this species is an interesting question, and, I am inclined to think, is directly connected with the origin of the treeless plains of those western regions. If, as I have intimated, it is a variety of C. femur-rubrum, it is highly probable the latter appeared first in the older districts of the Atlantic area in its present or some earlier form, and gradually extended west, and, as is usual with the group to which it belongs, as it ascended to the colder regions of the Rocky Mountain Range, would have assumed the shortwinged form, unless prevented by some compensating cause. The repeated burnings of the prairies may have caused frequent removals, and thus have given origin to its longer wings and migrating disposition. I am aware the question may be asked, Why did not the same thing occur with other species? But if the reader will carefully examine the list and localities of the United States Acridii, he will find but few species which belong to both the eastern and western regions; the belt which once formed.the water-line north and south through the continent forms a more distinct line between Acridian districts than even the Rocky Mountain Range, as I have shown in a former paper. But this is a question requiring a more thorough investigation than I can give it in this note, even had I the data necessary and felt able to do so with my limited geological knowledge. I therefore simply throw out the thought, to call the attention of others to the subject. There is another fact presented this season in regard to this group of the Calopteni, to which I wish for a moment to call attention. As shown in my Synopsis, and as confirmed by other entomologists, the chief difference between the spretus and femur-rubrum is the notch in the last abdominal segment of the male in the former and its absence in the male of the latter species, and the longer wings of the former. Heretofore, the femur rubrum, as thus marked, has always been our most common species in this section (Southern Illinois), and could, throughout the summer and fall and even during the spring, be found at any time in the fields and along the highways; but, strange to say, this season that form has entirely disappeared, and has been replaced by a rather more slender form, with the last segment distinctly notched and the wings lengthened, resembling, and apparently identical with, Professor Riley's C. atlanis. How are we to account for this? It will not do to call it a hybrid between the spretus and the femur-rubrum, as the former has never been known to visit this region, at least in numbers sufficient to attract attention, the great army last season having penetrated but a short distance into the western side of Missouri. Nor will it do to say my examinations have not been sufficiently thorough, for I have kept watch of them during the entire summer, gathering hundreds, and, although finding some variation, have failed so far to find a single femur-rubrum. I am also informed, by a letter just received from Professor Burril, of the Industrial University at Champaign, in this State, that since he noticed an article I recently published on this subject, he has paid some attention to the matter, and finds the same thing true there. I also observe a note in the last number of the American Naturalist, from Dr. Packard, mentioning the occurrence of spretus (probably atlanis) in Massachusetts. Also the very fact that Professor Riley last year mentions the intermediate form, which he names as a new species, and which had never before attracted attention, coincides with the other facts I have mentioned. Here, then, beyond dispute, a remarkable change is taking place, which gives rise to a number of important questions. And first of these is, What is the cause of this? I think it is owing chiefly, if not entirely, to climatic influences, and forms an index to the great changes in specific characters which may be effected by a change of climate. If I am correct in this, it follows that when the climate reverts to its normal condition the species will do the same; and, on the contrary, if one should be permanent the other will also, in all proba bility, be the same. I may also notice, as bearing upon this point, the fact (for since the publication of my recent article I have ascertained it is a fact) that Caloptenus differentialis Thos. has been seen in the central part of this State flying in bodies at considerable height, and apparently migrating. Acridium emarginatum Uhl., a Western species, never before known to occur east of the Mississippi, has been discovered this season as far east as Bloomington in this State. These facts are certainly important and instructive, and deserve careful consideration. The chief practical questions connected with this subject, and which more directly concern our agriculturists, are these:-(1) Will invasions of the C. spretus grow more and more frequent? (2) Will it continue to extend its limits farther and farther eastward? (3) Will the changes now taking place result in producing migratory hordes in our midst? To the first of these questions we may answer briefly, the spread of the population has brought these irruptions more into notice than formerly, and from this cause they appear more frequent. But this does not fully account for all the facts, and therefore we must suppose that a succession of similar climatic conditions has caused more frequent migrations; and that with the changes in this respect there will be a corresponding change in the effect. In answer to the other questions, we may state that unless there should be a remarkable permanent change in the climate, we need have no fears of such results. ART. XXII.-ON THE HEMIPTERA COLLECTED BY DR. ELLIOTT COUES, U. S. A., IN DAKOTA AND MONTANA, DURING 1873-74.* Odontoscelis pulicarius, GERMAR, Zeits. vol. i, p. 39, No. 6. Inhabits Dakota, and is found to be widely distributed throughout Eastern North America, from near Quebec to as far south as Galveston, Tex. Scutellera æneifrons, SAY, Long's Exped. Appendix, p. 229, No. 2. Obtained near Pembina, Dak., and from the vicinity of Mouse River, August 29, 1873. Subfamily EURYGASTRINA. 3. Eurygaster alternatus. EURYGASTER, Lap. Tetyra alternata, SAY, Amer. Entomology, vol. i, p. 43, tab. 3, fig. 3. Collected from the prairies near Mouse River, August 29, from near Pembina, from Turtle Mount, Dakota, and from the Milk River region in Northern Montana. 4. Sehirus cinctus. CYDNIDE. SEHIRUS, Amyot & Serv. Pentatoma cincta, PALISOT-BEAUV. Ins. Afr. et Amér. p. 114, pl. 8, fig. 7. Found near Pembina, and near Mouse River on August 29, 1873. * [See note, p. 481, anteà.—ED.] |