U N 1 VE.R.5ITY or I LLl NOIS vSlO.a BIOL** Return this book on or before the Latest Date stamped below. A overdue charge is made on all books. T ., University of Illinois Library -ftb-G Mk JUN 'ML— M32 Digitized by the Internet Archive in 2011 with funding from University of Illinois Urbana-Champaign http://www.archive.org/details/turtlesofillinoi16cahn ILLINOIS BIOLOGICAL MONOGRAPHS Volume XVI PUBLISHED BY THE UNIVERSITY OF ILLINOIS URBANA, ILLINOIS EDITORIAL COMMITTEE John Theodore Buchholz Fred Wilbur Tanner Harley Jones Van Cleave no. s- TABLE OF CONTENTS Nos. 1-2. The Turtles of Illinois. By Alvin R. Cahn. No. 3. The Phylogeny of the Hemiptera, Based on a Study of the Head Capsule. By Charles Stockman Spooner. No. 4. A Classification of the Larvae and Puparia of the Syrphidae of Illinois. Exclusive of Aquatic Forms. By Elizabeth M. Heiss. ILLINOIS BIOLOGICAL MONOGRAPHS Vol. XVI Nos. 1-2 Published by the University of Illinois Under the Auspices of the Graduate School Urbana, Illinois 1937 EDITORIAL COMMITTEE John Theodore Buchholz Fred Wilbur Tanner Harley Jones Van Cleave UNIVERSITY OF ILLINOIS 1000—8-37—9888 I PRE33 ii THE TURTLES OF ILLINOIS WITH 31 PLATES, 20 MAPS, AND 15 TEXT-FIGURES BY Alvin R. Cahn Contribution from the Zoological Laboratory of the University of Illinois No. 492 PREFACE For a number of years the writer has had in mind the production of a monograph dealing with the turtles of Illinois, if for no other reason than the fact that they have, as a group, been much neglected throughout the middle west. In most herpetological literature of the region much space has been given to snakes, salamanders, and frogs, but turtles have received at best a mere mention, being passed off with the enumeration of a species or two in a given locality. This is perhaps due to the diffi- culty of capturing specimens, coupled with the uncertainty of identifying most species as they sit sunning themselves in security on a log in the middle of a pond, and the very awkward problem of keeping such bulky creatures once they are captured. I suspect, however, that it is also in r» part due to the fact that there is really very little literature available to the average student or held collector which will enable him to identify with ease and certainty a species once he catches it. Keys there are, but are many are located in old publications not everywhere available ; many so highly technical as to require an advanced knowledge of comparative anatomy for their comprehension and use ; others are too superficial and general to be of really practical value. It has been the writer's plan, therefore, to present a paper dealing with the various species of turtles found within the boundaries of Illinois, this paper to include keys to the families, genera, and species—intelligible to readers who are not profes- sional herpetologists—together with a full discussion of the life history of each species so far as it is known. Such a discussion must also con- tain a detailed description of the adult and young, eggs, habits, economic importance, food habits, sex differentiation, and parasites, in order to approach completeness. One real drawback, as the writer sees it. to the ready identification of turtles, is the lack of adequate photographs that will in themselves be an aid ( and not a handicap ) in the determination of the identity of the species. To that end he has bent every effort to illustrate the present paper with the best photographs he could obtain. All the illustrations are original and have been made especially for this monograph. The photographs are either from living specimens or from freshly preserved material, in the latter case photographed within an hour after killing so as to insure full color values. The writer has drawn freely upon available literature, as will be seen on consulting the bibliography. This bibliography has been arranged under several headings so as to make it of greater use to both the ama- teur and the professional student. 6 ILLINOIS BIOLOGICAL MONOGRAPHS The Illinois State Natural History Survey, under the direction of Dr. Theodore H. Frison, has placed at the writer's disposal its collections of Illinois turtles. Unfortunately, the original collection made by Profes- sor H. Garman in 1888 for the State Laboratory of Natural History has disappeared and hence has not been available for study. This has proved to be a serious handicap, for the writer has been unable to obtain speci- mens of several species listed by Garman from Illinois. To Dr. David H. Thompson and Mr. Francis D. Hunt, of the Natural History Survey, the writer expresses his appreciation for their assistance in procuring specimens for examination from various parts of Illinois, and to the com- mercial fishermen who have sent in many sacks and barrels full of live turtles for study, the writer owes in large measure the information con- cerning the geographical distribution within the state. During the sum- mer of 1931, Mr. Joe D. Combs, of the Zoology Department of the Uni- versity of Illinois, spent two months under the writer's direction, on the Illinois River at Meredosia, collecting information on life histories and obtaining many interesting facts. To the many friends all over the country who submitted material for comparison and for study, and to the American Museum, the Field Museum, and the United States National Museum, the writer expresses his deep appreciation for all courtesies rendered. CONTENTS Illinois Topography and Hydrography 9 Historical Review 16 Key to the Families of Illinois Turtles 20 Key to the Family Chelydridae 20 Key to the Family Kinosternidae 20 Key to the Family Testudinidae 21 Key to the Family Trionychidae 22 Family Chelydridae 23 Genus Macrochelys 23 Macrochelys temminckii 24 Genus Chelydra 34 Chelydra serpentina 34 Family Kinosternidae 46 Genus Sternotherus 46 Sternotherus odoratus 47 Genus Kinosternon 56 Kinosternon flavescens 56 Kinosternon subrubrum subrubrum 62 Family Testudinidae 67 Genus Clemmys 68 Clemmys guttata 68 Genus Emys 75 Emys blandingii 75 Genus Terrapene 83 Terrapene Carolina Carolina 84 Terrapene ornata 96 Genus Graptemys 103 Graptemys geographica 105 Graptemys pseudogeographica pseudogeographica 113 Genus Chrysemys 122 The Chrysemys Problem 123 Chrysemys picta marginata 129 Chrysemys picta bell ii 138 Chrysemys picta dorsalis 145 Genus Pseudemys 152 Pseudemys concinna 152 The Pseudemys elegans-troostii Problem 159 Pseudemys troostii 160 Melanistic Males 169 Family Trionychidae 175 Genus Amyda 175 Amyda mutica 176 Amyda spinifera 184 CONTENTS (Concluded) Hypothetical List 194 Sternotherus carinatus 195 Chrysemys picta 199 Amyda ferox 199 Chrysemys treleasei 200 Pseudemys hieroglyphica 201 Clemmys insculpta 203 Bibliography 208 Illinois References 208 General References 209 References for Adjacent States 212 References for Synonymy 214 Glossary 217 ILLINOIS TOPOGRAPHY AND HYDROGRAPHY The state of Illinois occupies a unique position geographically in the United States, for within its borders many of the major faunal and floral features of the east and west, the north and south, join and to some ex- tent overlap or intergrade. Here representative species of the eastern forests and the western prairies, of the northern and southern forests, come together, and meet with the species of the sand dune region of Lake Michigan. Hence, as one might expect, the biota is varied and rich. Illinois is essentially a prairie state, but about 42 percent of its total area, or about fifteen million acres, is classified ecologically as having been originally deciduous forest of various types. This great forest, before being destroyed by man, covered most of the southern third of the state, as well as the northeastern section. Here roamed the white-tailed deer (Odocoileus virginianus), the black bear (Euarctos americanus), timber wolf (Canis lycaon), gray fox (Urocyon cinereoargenteus), and red fox (Vulpes fidva). The remaining region, approximately 58 percent of the total area, was of parkland formation: grass prairies, with clumps of trees scattered through it. With the colonization of the state and its phenomenal growth in population, the forested region was reduced, until at present it is represented by less than 3,000,000 acres. With the deforestation came the cultivation of the land, and this was sub- sequently accompanied by drainage. The present biota is the product of these changes. Deforestation automatically and directly eliminated the larger species of forest animals, while the indirect effects of deforestation —cultivation and drainage—have had a profound influence upon the aquatic biota. The deforested land can no longer hold its original quota of water, and hence the run-off is rapid and sudden and spasmodic, re- sulting in floods and in a diminution of the volume of the rivers. There is no possible way in which we can with certainty reconstruct the original faunal distribution within the state, especially in respect to such a group as the turtles, but certain it is that the original distribution of animals was quite different from that which we see to-day. And it requires no prophet to predict that the future holds an even more profound change. Illinois is essentially a plain, gently rolling in places, in others flat. It is the lowest (average elevation 600 feet) of all the north-central states, lying in the middle of the great interior basin of the North Ameri- can continent, which is bounded on the east by the Appalachian and on the west by the Rocky Mountains. In general, the elevation decreases from north to south and from east to west, but this is in no sense a regu- 10 ILLINOIS BIOLOGICAL MONOGRAPHS lar decline. The two essential features which interrupt the plain surface of the state are (1) the moraine features of the drift area, and (2) the rock ridges.