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the occurrence of Trimicra pilipes, apparently identical with the European and probably with the Yorth American T. anomala, although the latter is comparatively rare in the Eastern States, while T. pilipes is exceedingly common in all California in winter.

In the whole western region, the genera Tabanus and Chrysops seem to be far less abundant in species than in the region east of the Mississippi.

Of the anomalous family Blepharoceridae, all the species of which seem to be rare and local, I have described a species from Yosemite Valley and a new genus from the Rocky Mountains.

After having detailed the peculiarities of the western, and especially of the Californian, Dipterous fauna, it remains for us to examine what they have in common with the eastern fauna. As a rule, cases of specific identity between those regions occur more frequently in those same families in which cases of specific identity are more frequent between Europe and North America. Sereral Californian Limnobice are not distinguishable from eastern species. Trimicra pilipes, already mentioned, and Symplecta punctipennis, seem to be species of nearly universal occurrence. Several Syrphida, common in the Eastern States, also occur in California. Asilide and Tabanilla, on the contrary, seem to be different in both regions, just as no species of these two families is as yet known to be common to North America and Europe.

The genera Ceraturgus, Nicocles (Asilida), Triptotricha (Leptida), and the singular Epibates (Bombylidae), are worth noticing as being common to both sides of North America, and not found yet outside of that continent. The remarkable genus Rachicerus (Hylophagida) belonged in the same category, until recently, when it was found in Spain.

In the mountain ranges which cross the western region from north to south, some northern and subarctic genera and species are able to reach very far south, and thus to come in contact with the forms of the local fauna. In Yosemite Valley, at an altitude of 4,000 feet, the mixture of truly Californian forms with those peculiar to the Sierra is only beginning, the latter being comparatively rare. Around Webber Lake, that is, farther north, and at an altitude of 7,000 to 8,000 feet, Californian genera and species still occur in abundance, but more northern forms are frequently met with them. The northern genus Scellus (Dolichopodida) occurs alongside of the Californian Eulonchus (Cyrtide). With the Californian Dasyllis astur (Asilida) and Laphria vultur (id.), I found Laphria rapax (id.), which looks like a northern form, although I may be mistaken in my surmise. The specimens of Dasyllis astur, found at that altitude, have much more yellow pile on their legs, neck, and pleura than those which were taken but little above sea-level. According to the same law, Dasyllis flaricollis Say, which ranges from Canada to Texas, has much more yellow on its legs and pleure in the north than in the south. Many interesting species were found round Webber Lake :

I will name a new Tachytrechus (Dolichop.), related to T. mochus of the Eastern States, which I used to find abundantly near the Trenton Falls, New York; a new Sphecomyia (Syrphidae), a remarkable genus, of which only two species were hitherto known, one in Europe and the other in North America, and those two may yet turn out to be identical; thirteen species of the genus Cyrtopogon (Asilido), eleven of which were undescribed, and some of them remarkably handsome (in Dr. Schiner's Catalogue of Asilida, published in 1866, only thirteen species of Cyrtopogon are enumerated for the whole world). The other orders of insects afforded the same interest. Parnassius was very common ; two new species of Cicada were found, etc.

Of the fauna of the Rocky Mountains, I had occasion to speak in another place (Report on the Diptera collected by Lieutenant Carpenter in Colorado in 1873, in the Annual Report of the United States Geological and Geographical Survey of the Territories for that year). The relationship of the fauna in the higher regions of those mountains to that of the northern latitudes of the continent is much more marked than that of the fauna round Webber Lake in the Sierra. A series of char. acteristic northern forms were found in Lieutenant Carpenter's collection :-Hesperinus brerifrons (Bibionidee), which had been received from Mackenzie River and collected by myself on Mount Washington; Arctophila flagrans, Tipula macrolabis, Helophilus bilineatus, etc. For want of time, I did not collect much in the Rocky Mountains, but was struck by the frequent occurrence, near Georgetown, Colo. (8,500 feet altitude), of a species of Dejeania (Tachinidae), a genus which was hitherto received from South America and Mexico. Near Manitou, Colo. (altitude 6,400 feet), another very large and peculiar Tachinid occurred, of which I also have specimens, collected by Mr. Cleveland near San Diego.

Such facts, as well as many others mentioned in the course of the present paper, prove that there is a great deal to be learned yet about the laws regulating the geographical distribution of insects. In the mean while, it is useful to keep such facts in view by singling them out from the arid mass of descriptive entomology.



[PLATES 27, 28.]


BALTIJORE, January 1, 1977. DEAR SIR: The results of my observations and collecting during the two weeks that I was enabled, through your courtesy, to spend on the plains and mountains of Eastern Colorado, are embodied, as far as possible, in the following pages.

Although much hindered by rains, hail, and snow-storms, I was able to extend rapidly a series of collecting trips from Denver, and a few miles north of it as far as the Grand Cañon of the lrkansas River, a few miles west of Cañon City. In all the sections visited, I had no occasion to complain of the scarcity of insect life. Indeed, in such places as were moderately supplied with water, either in the cañons of the mountains or on the farms and lands adjacent to the creeks and irrigating canals, many kinds of insects were as abundant as we find them to be in corresponding situations in the Atlantic States. It was only in the perfectly desert spots which afforded no sustenance for vegetation that an absence of these creatures was to be noted. nl examination of the country in and adjouing Denver, particularly on the west side, showed that the common weeds of the eastern division of the continent had already established themselves there, and that, as was to be expected, many of the common insects dependent upon them were present in abundance. On the open commons of the suburbs of Denver I was delighted to see large patches of showy flowers, and to observe how cortain insects of similar colors flew to and rested upon them. Very conspicuously was this the case with a delicately blue Lupin, with fine large heads, which occurred in rast numbers near a mill-race running through à low part of the plains. Two species of the little bluets, Lycana melissa and L. rapahoe, settled upon these flowers, and when at rest were verymdifficult to recognize. Danais archippus Cramer was widely distrib. uted, except in the high mountains, and was generally observed to be mat

ing. It was common in most places away from the mountains, but less common in Clear Creek Cañon, in the Ute Pass and adjoining gulches, and in the Cañon of the Arkansas. Specimens were to be seen along the route from Baltimore all the way to Kansas City; while in Eastern Kansas it seemed to be more abundant than anywhere else. On the treeless plains, it and all other large flying insects, excepting the grasshoppers and dragon-flies, ceased to appear until we reached the vicinity of water and cultivated lands, when it was again seen on the wing, ilying with its wonted rigor.

In the Clear Creek Cañon and adjactent gulches, the large and showy Papilio daunus Boisd. was flying rapidly and agitatedly over the water, as if seeking for a plant upon which to deposit its eggs. One specimen was also noticed in the Ute Pass on August 13. All of them were too restless to admit of capture, and at no time were they within reach of my net. At the same time and in the first-mentioned place, Pieris oleracea, Vanessa antiopa, Limenitis weidemeyeri in very fresh condition, a large Argynnis, Colias eurytheme, and a small Melitæa, were either seen or captured. A very fine large Satyrus was tolerably common in Bea. ver Brook Gulch, and another species occurred in the gulch near Manitou. Colias eurytheme and Pieris protodice were abundant near Denver and eren in the city, flying upon the flowers of an Euphorbiaceous plant which bears leares margined with white.

Mothing was conducted with success in the station at the mouth of Beaver Brook, and, but for my short stay, great numbers and many species of Geometrids and other Heterocera might have been readily acquired.

Coleoptera of many species were readily taken both on the plains and in the mountains. Several kinds, such as Epicauta ferruginea Say, Cicindela punctulata Fab., Chauliognathus basalis Lec., Eleodes obsoleta Say, and Asida opaca Say, were found in almost all places on the plains at a short distance from the mountains. The former occurred in large numbers upon the flowers of Helianthus and other plants with yellow flowers, although in a few cases it was met with upon the white blos. soms of the Euphorbia. Cicindela punctulata was common upon black muddy patches in Bearer Brook Gulch and in Clear Creek Cañon. It was very variable, and generally of the greenish color, with the white spots and lunules large. Specimens seen in and around Denver were all of the black-bronze type, with very small white niarkings. Those of the alkaline soils of the region near Cañon City were the most brilliant and highly metallic in their color. Cicin:lela pulchra Say was found singly upon blackish sand near the Arkansas River, August 11, at a distance of about one-half of a mile from the mouth of the Great Cañon. It was very wary, and of the variety with scarcely perceptible markings. Chauliognathus basalis Lec. was quite common upon sunflowers, chiefly upon the plains and near the foot-hills. It seemed to furnish about two distinct types, both of form and marking, the former having varieties

more numerous than the other. Those of Denver were generally large and stout, with the tuoras longer, more roundexl, and reflexed anteriorly, and with the discoidal black spot alınost always broken into several parts, or divided down the middle. Those from Bijou were of the same type. The specimens from Colorado Springs and south ward occurred almost invariably on a bushy weed bearing, densely packed, small yellow flowers. They were narrow, close-set, with the thorax truncated in front, and the anterior margin evenly turned up, the disk dull, the black spot entire and covering all but the margins, and with antennæ flattened. Eleodes obsoletus occurred under rubbish and dried dung, and around the base of Yucca and Cacti. It extended all the way from Denver to Cañon City on the hill-sides, and was most abundant between Colorado Springs and the Garden of the Gods. It was variable in all the localities, but most so near the last-named city. Eleodes hispilabris and. E. extricata first occurred to me near Colorado Springs, and from thence extended southwardly to Cañon City. I did not meet with any specimens near Denver, nor at Golden, nor anywhere within the limits of the mountains. Eleodes suturalis Say was rare and found only near Denver. Eleodes tricostata Say was not seen elsewliere than between Colorado Springs and the Garden of the Gods; but the specimens found nearest to the mountains were more flattened, and had the costal margin of the elytra more prominently recurved. Eleodes nigrina Lec. was rare, and taken only in Manitou Park. Two specimens of Asida elata Lec. were found running among the grass in the evening twi. light, the one near Colorado Springs and the other a short distance west of Cañon City. Asida opacu Say was tolerably common and quite rariable in the width of its thorax and elytra and in the amount and prominence of the reticulations of the surface of the latter.

Of the Erotylidae, Cypherotylus boisdurali Chev., occurred only in Clear Creek Cañon. It was crawling on the surface at a considerable elevation above the bed of the creek, and in the midst of the pine woods, where there was bark and rubbish upon the ground. The closest scrutiny failed to detect more than a single specimen, and I was induced to believe that the season was too far advanced for its appearance in the usual numhers.

Meloidae were not numerous in species, but Epicauta ferruginea Say was abundant everywhere, in the mountains and cañons and on the plains. The sunflowers and thistles were sometimes crowded with them, but generally only two or three were at once upon a single flower. It was very variable in size, ranging from 6 to 10 millimeters in length. Usually it affected the yellow flowers, which corresponded well with its color; but occasionally it was quite as abundant upon the white flowers of the Euphorbia and other similar plants. Dwarf specimens were quite common, and frequented the same places as the large

In this connection, however, it should be borne in mind that the summer was a remarkable one, with rery variable degrees of tempera


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