United States National Museum

\ \ SMITHSONIAN INSTITUTION UNITED STATES NATIONAL MUSEUM Bulletin 168 NEARCTIC COLLEMBOLA OR SPRINGTAILS, OF THE FAMILY ISOTOMIDAE BY J. W. FOLSOM UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1937 For sale by the Superintendent of Documents, Washington, D. C. ---------- Price 30 cents ADVERTISEMENT The scientific publications of the National Museum include two series, known, respectively, as Proceedings and Bulletin. The Proceedings series, begun in 1878, is intended primarily as a medium for the publication of original papers, based on the collections of the National Museum, that set forth newly acquired facts in biology, antliropology, and geology, with descriptions of new forms and revisions of limited groups. Copies of each paper, in pamphlet form, are distributed as published to hbraries and scientific organi- zations and to speciahsts and others interested in the different sub- jects. The dates at which these separate papers are pubhshed are recorded in the table of contents of each of the volumes. The series of Bulletins, the first of wliich was issued in 1875, contains separate publications comprising monographs of large zoologi- cal groups and other general systematic treatises (occasionally in several volumes), faunal works, reports of expeditions, catalogs of type specimens and special collections, and other material of similar nature. The majority of the volumes are octavo in size, but a quarto size has been adopted in a few instances in wliich large plates were regarded as indispensable. In the Bulletin series appear volumes under the heading Contributions from the United States National Herbarium, in octavo form, published by the National Museum since 1902, which contain papers relating to the botanical collections of the Museum. The present vrork forms No. 168 of the Bulletin series. Alexander Wetmore, Assistant Secretary, Smithsonian Institution. Washington, D. C, May 15, 1937. CONTENTS Page lutroduction 'l 1 Notes on the evolution of the mucrones 3 Phylogenetic and taxonomic notes 4 Definitions 7 Family Isotomidae 7 Key to genera of Isotomidae 8 Genus Tetracanthella 10 Genus Anurophorus 12 Genus Folsomides 13 Key to species of Folsomides 14 Genus Isotomodes 16 Genus Folsomia 19 Key to species of Folsomia 19 Genus Guthriella 33 Key to species of Guthriella 33 Genus Proisotoma 38 Key to subgenera of Proisotoma 38 Subgenus Ballistura 39 Key to species of Ballistura 39 Subgenus Proisotoma 43 Key to species of Proisotoma 43 Genus Archisotoma 66 Genus Agrenia 68 Genus Isotomurus 70 Genus Isotoma 78 Key to subgenera of Isotoma 78 Subgenus Pseudisotoma 78 Subgenus Vertagopus 81 Key to species of Vertagopus 81 Subgenus Isotoma 87 Key to species of Isotoma 87 Unidentified species 116 Literature cited 120 Explanation of plates 129 Index 141 III — NEARCTIC COLLEMBOLA, OR SPRINGTAILS, OF THE FAMILY ISOTOMIDAE By J. W. FoLsoM^ INTRODUCTION Though all the known Nearctic species of Collembola of the family Isotomidae are considered in this paper, our fauna undoubtedly contains many additional ones. Of the 66 species and 16 varieties herein treated, 28 species and 2 varieties are described as new. Of the Nearctic forms, 21 species and 9 varieties are also Palearctic in distribution. Specimens of most of the Nearctic species have been compared with Palearctic specimens, not only by me but also by my European colleagues, with whom I have been exchanging material for more than 30 years. I have studied nearly all the type specimens of Isotomidae described from North America, notably those of Packard, MacGillivray, and Guthrie. When living in Cambridge, Mass., I made descriptions and drawings from the Packard collection of Collembola in the Museum of Comparative Zoology, through the courtesy of Samuel Henshaw. This collection consisted mostly of the material described by Packard (1873) in his "Essex County" paper. This paper had no illustrations, but in the course of its preparation Dr. Packard made a great many pencil drawings, which he gave to me, and these have been a useful aid to the recognition of the species that Packard described. *Dr. JtrsTUS Watson Folsom, the author of this bulletin, died at Vicksburg, Miss., on September 24, 1936, at the age of 65, shortly after the manuscript was sent to the printer. A native of Massachusetts, Dr. Folsom was an entomologist of wide training and experience. Since 1925 he had been associated with the United States Department of Agriculture as entomologist, prior to which he taught entomology at the University of Illinois for nearly a quarter of a century. At the time of his death he was stationed at the Cotton Insect Laboratory of the Bureau of Entomology and Plant Quarantine at Tallulah, La. Though accomplished in many branches of entomological science, including anatomy and ecology as well as taxonomy, Dr. Folsom became a world-famous authority on the orders Thy- sanura and Collembola and published many papers dealing with these primitive insects. The present monograph, on the Isotomidae, is one of the most exhaustive studies of any group of Collembola ever undertaken and serves as a fitting climax to the author's long career as a biologist. Editor. 1 2 BULLETIN 168, UNITED STATES NATIONAL MUSEUM In addition, I collected in eastern Massachusetts, including Essex County, most of the species that Packard described from that region, and compared them with liis types. Of the MacGillivray (1896) cotypes and other specimens of Isotoma, I have studied three sets: The collection of the Aluseum of Com- parative Zoology; the collection of Cornell University, through the courtesy of Prof. C. R. Crosby; and a set of specimens given to me by Dr. MacGillivray. Guthrie's (1903) types and other material were kindly loaned to me by Prof. H. F. Nachtrieb, and many additional specimens were received from Dr. Guthrie. The entire collection of Prof. F. L. Harvey, with his notebooks, I bought from Mrs. F. L. Harvey. The Apterygota of the California Academy of Sciences described by Schott (1896a) were destroyed by fire, so I was informed by the secretary of that institution. Important among large collections received for study were those of the Illinois State Natural History Survey, through the courtesy of C. A. Hart and Dr. T. H. Prison; the New York State Museum, through S. C. Bishop and D. B. Young; the American Museum of Natural History, through Dr. F. E. Lutz; and Stanford University, through Prof. V. L. Kellogg. From California, collembolan material in abundance came from the late Prof. C. F. Baker, Prof. E. O. Essig, and A. P. Morse. From Oregon, a large collection was received from Dr. H. E. Ewing, and from Florida one from Prof. T. H. Hubbell. From Iowa, specimens in abundance were contributed by C. N. Ainslie, and from Tennessee many by G, G. Ainslie. Much Pennsylvania material came from Dr. H. A. Surface, and a great number of New York specimens from Dr. M. D. Leonard, Prof. C. R. Crosby, Dr. H. Glasgow, Prof. J. D. Hood, and E. A. Maynard. For Canadian species acknowledgments are due to Prof. E. M. Walker, and especially to Charles Macnamara, who has for many years been sending me a wealth of material. The greater part of the material used, however, I collected, chiefly in Massachusetts, Ohio, Illinois, Wisconsin, and Louisiana. The omission of a collector's name in the data concerning specimens means that they were collected by me. Similarly, the omission of refer- ences (in parentheses) to the ownership of specimens indicates that they are in my collection. The illustrations, made by me, were drawn from type specimens when possible. The most important part of the material studied has been given to the United States National Museum. COLLEMBOLA OF THE FAMILY ISOTOMIDAE d NOTES ON THE EVOLUTION OF THE MUCRONES A comparative study of the diverse forms of miicrones found in Isotomidae leads to the inference that some of the forms have been derived from others. The present account by no means exhausts the subject. It consists simply of such conclusions as came to mind during my systematic study of Isotomidae. A primitive type of mucro is found in Guthriella, essentially the same form that occurs in several species of Achorutes} In Guthriella vetusta, for example (pi. 10, fig. 104), the mucro is like that of Achorutes socialis in its apical tooth, anteapical tooth, and outer and inner lamellae extending from the anteapical tooth to the base of the mucro. In Ballistura the mucro remains fundamentally as in Guthriella. With this generalized type of mucro as a basis, we may infer, by comparing the various forms of mucrones with one another, that specialization of the mucro has occurred in three main ways, as follows: 1. Lamellar development. The two primarj^ lamellae may increase in size, and new lamellae may be added. Extreme conditions of lamellar development are shown in schdferi (pi. 17, figs. 173, 174) and rainieri (pi. 16, figs. 164-167). In the complex mucrones of these species the apical tooth, anteapical tooth, and outer and inner lamellae are evident, but additional lamellae are present, with additional teeth for their support. The extra lamellar expanse is corre- lated with a superaquatic habit. 2. Addition of teeth. The species titusi (pi. 18, figs. 186, 188) shows the primitive pair of lamellae and the tv%'o primary teeth, with an added third tooth, supporting a lamella. This third tooth, lateral in position and anterior to the anteapical tooth, occurs in many species of the family. The fourth tooth, as in commvna (pi. 17, fig. ISO) is never lateral but is usually in line with the first and second teeth. In sepulcralis the mucro, normally tridentate (pi. 20, fig. 213), is occasionally quadridentate (pi. 20, fig. 214) as an individual variation. Many other species have four teeth normally.

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