ART. XIII -WESTERN DIPTERA : DESCRIPTIONS OF NEW GEN- ERA AND SPECIES OF DIPTERA FROM THE REGION WEST OF THE MISSISSIPPI AND ESPECIALLY FROM CALIFORNIA. By C. R. Osten Sacken. PEEFACE. The Bipteraoi the Pacific coast are at present almost unknown. A few species picked up during the visit of the Swedish frigate Eugenia, probably in the environs of San Francisco, and described by Mr. Thom- " son ; some four dozen species, j)ublished by Mr. Loew in his Centurise "; a few other species, by Dr. Gerstaecker; and two lAmnobice, by me, con- stitute about all we know of Californian DijHera. Even Chili is, in this respect, much better explored, with the 556 species contained in Dr. Philippi's publication. In the present publication, I give a survey of the collection of Diptera which I formed during my recent western journey, and describe the most remarkable forms. The majority of the species described belong to California, where I collected the most ; the fauna of Colorado and of the vast intermediate region will come in the second line only, the materials being less abundant. However, the more I proceed with my study, the more I am impressed with the fact that the western fauna is essentially one, and that many of the characteristic forms of California sooner or later will turn up in Colorado. The times and places of my collecting in California are as follows : During the winter months (January to March, 1875), I collected a little in Southern California ; my most active collecting, however, was confined to the months of April and May, 1876, in Marin and Sonoma Counties; a few days in Yosemite Yalley in June; and a couple of weeks in the Sierra Nevada in July, especially about Webber Lake, Sierra County. What I brought together is therefore but a small fragment of the fauna, collected during a very limited season. And, yet, even this fragment yields some very interesting facts concerning the geographical distribu- tion of insects, discloses unexpected analogies and coincidences between the fauna of California and those of Europe, Chili, and even Australia, and unforeseen differences from the fauna of the Atlantic States. To such facts, bearing upon the geographical distribution of insects, I pay especial attention in the introductory paragraphs to each family; and, at the end, I give a general survey of the results obtained. For the fauna of Colorado, I availed myself of very valuable mate- rials kindly contributed by Mr. P. E. Uhler, Dr.A. S. Packard, and 190 BULLETIN UNITED STATES GEOLOGICAL SURVEY. Lieut. W. L. Carpenter. Here and there I have introduced descriptions of some remarkable species from the Atlantic States. In treating of the Californian fauna (or flora) it must be borne in mind that what is called Sierra Nevada is not only a mountain range, but a whole country—a high plateau from 6,000 to 8,000 feet above sea- level, forming a long and comparatively broad belt of land, with its lakes, rivers, forests, and plains—an upper story of California, partaking of some of its products, but on the whole entirely different. For the better undestanding of the facts bearing on the geographical distribu- tion of insects, I will state here, once for all, that my collections about Summit, Sierra Nevada, and Webber Lake were formed at an altitude from 7,000 to 8,000 feet above sea-level; that the altitude of Lake Tahoe is 6.200 to 6,300 feet, and that of Yosemite Valley about 4,000 feet. My collecting grounds in Southern California, as well as in Marin and So- noma Counties, were all at comparatively low levels, except the Gey- sers, Sonoma County, which are about 3,000 feet above sea level. It is not my intention to describe all the western Diptera which I pos- sess or can get hold of. Always keeping the higher aims of science in view, my effort will be to contribute toward those aims. The detailed de- scription of special entomological faunas must of necessity be left to local students. An outsider, a transient collector and describer, has to keep their interest in view, and to try to pave the way for them rather than to block up their progress by an indiscriminate and aimless publication of new species. In prefixing diagnoses to some of my descriptions, my aim was to en- able the reader at a single glance to get hold of the principal features of the described species, and thus to save his time in the work of iden- tification. Such a diagnosis, in order to be useful, must be short, even at the risk of being applicable to more than one species. Wherever the species in a genus are more numerous, I prefer to give an analytical table. The attempt of some authors to draw diagnoses which are tanta- mount to definitions of the species is very difficult to carry out, espec- ially in the larger genera ; such diagnoses finally become as long as the descriptions themselves, and therefore practically useless. In quoting species described in North American publications or in Dr. Loew's "Centuries", I will simply refer to them without repeating the descriptions, as it is to be expected that a dipterologist is in possession of the works thus quoted. In some cases I will reproduce or translate descriptions which are less easily accessible. All the type specimens of these my papers I intend to deposit, for future reference, in the Museum of Comparative Zoology in Cambridge, Mass., where my former dipterological collections are also to be found ; the few exceptions will be mentioned in their place. I owe a special tribute of gratitude to Mr. Henry Edwards, of San Francisco, for his manifold assistance, as well as for the contribution of valuable specimens. ; OSTEN SACKEN ON WESTERN DIPTERA. 191 Families CULICIDiE, CHIRONOMID^, PSYCHODID^. Half a dozen species of Cidex, two Anoplieles^ and two Gliironomus are among my collections from California. They all exhibit the characters and coloring peculiar to the species of these genera in other countries. A Culex from Southern Oaliforuia is distinguished by very sparsely bearded antennae of the male and a peculiar structure of the palpi. PSYCHODA sp.—A siugle specimen ; San Kafael, Gal. In the absence of any remarkable western forms, I describe two new species from the Atlantic States. The first belongs to the little known genus Aedes {CuUcicJce), of which only one si)ecies was known to occur in the United States. The other is a second species of the new genus Ghasmatonotus {CMronomidce) established by Dr. Loew for a species which I discovered in the White Mountains. Aedes fuscus u. sp., S 2 —Brown ; thorax clothed with a short, appressed, brownish-golden tomentum ; abdomen with whitish-yellow narrow bands at the base of the segments ; venter whitish-yellow. black and legs brownish, Antennae ; proboscis with a metallic reflection pleurae femora paler on the under side ; under the root of the wings with a spot clothed with whitish scales. Long. corp. 3-4'^'". Hah.—Cambridge, Mass., in May. Obs.—I bred this species from larvre which I found in a pool together with those of several species of Culex. The lar^?e and pupre behaved exactly like those of Culex, and only attracted my attention by their smaller size. If I could have known beforehand that they belonged to Aedes, I would have compared them more closely with the larvce of Culex. The metamorphosis of Aedes has never been observed before. Ghasmatonotus bimacui/Atus n. sp., <? .—Black ; wings of the same color and with two large white spots. Length about LS"""^. Black ; thorax shining ; base of the abdomen laterally pale greenish- yellow. Feet black ; front coxse and' all yellowish base of the femora ; the first tarsal joints are of the same pale yellowish color, except the tip, which is black. Knob of halteres greenish. Wings black; the first white spot is in the shape of a cross-band between the second vein and the anal angle; the second spot is square, and situated on the hind margin, within the fork of the fifch vein. Sa&.-^-Catskill Mountain House, in July, 1874; numerous male speci- mens Quebec (Mr. Belanger). ; The first posterior cell and the cell withiu the fork of the fifth vein are much longer here than in C. unimaculatus Lw., and the latter cell is larger and broader. Heuce it happens that although in both species the cross-band-like spot is placed immediately inside of the proximal end of the fork, it occupies the middle of the wing in C. unimaculatus^ and is much nearer the base in C. himaculatus. The abdomen of the male ends in a comparatively large and conspicuous forceps (the " hypojjygium maris glohosum " in Mr. Loew's description of C. unimacu- — ; 192 BULLETIN UNITED STATES GEOLOGICAL SUKVEY. latus seems to indicate a different structure ?). I found both species in the same situation, walking in numbers on the leaves of low shrubs. Family CECIDOMYID^. Of the numerous galls of Cecidomyice observed by me in California, I will mention only a few, of which I have kept a written record. On Juniperus californicus, fleshy, subglobular galls on the axis of the small twigs; when full grown, about two-fifths of an inch in diiame- ter, with a round opening at the top, the edge of which is from three- to five-lobed, the gall when ripe thus resembling the fruit of the Medlar {Mespilus) in shape; but, before being full grown and open, it is more like a diminutive melon or tomato, being furrowed longitudinally, like these fruits.