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Bulletin OF THE Illinois State Laboratory OF Natural History Urbana, Illinois, U. S. A. STEPHEN A. FORBES, Ph.D., L.L.D., Director Vol. X. May, 1915 Article VI. THE CHIRONOMID.E, OR MIDGES, OF ILLINOIS, WITH PARTICULAR REFERENCE TO THE SPECIES OCCURRING IN THE ILLINOIS RIVER John R. Malloch ERRATA Page 49, line 7 from bottom, page 69. line 8 from bottom, page 85, last line, and page 86, line 11 from bottom, for choiiuct'hrista read chaiiuvcristt]. Page 71, line 2 from bottom, for Tctraophthalmus, read Tetraopes. Page 75, line 3 (second column) below first heading, for Cistudo read Terrapene. Page 76, last line in first list, for brcvicaudis read brcvicauda. Page 87, line 2 (second column) below first heading, for carisce read cardisce. Page 214, lines 4, 7, and 11 above heading, for flaviciiigulata read flavicingula. Page 283, line 19 from bottom, for Simulidcc read Siiiiiiliida-. Page 289, line 7, for Bezzia read Probezzia. Page 409, line 23, after /i. read 5.^6. Page 531, line 12 from bottom, for dissimilis read nivoriundus. CONTENTS PAGE Intro.hiL-tion 217-289 Methods of collecting 277 >rothoils of rearing 278 Methods of preservation 278 Synonymy affecting family names 279 Biology and taxonomy 281 The egg stage 281 Larval characters 282 Food of the larva) 286 Characters of the pupa; 286 Characters of the imagines 287 Food of the imagines 288 Acknowledgments 288 Keys to subfamilies 289 Larvaj 289 Pupas 289 Imagines 290 Ccraiopngonintr 290-361 Larval characters 290 Tiipal characters 291 Tmaginal characters 292 Keys to genera 293 Larva; 293 Pupa; 293 Imagines 293 Keys to larva; and pupa; of North American species of Ceratnpogon and Fnrcipomyia 294 Addendum to CeratopoffonincF 360 Sup|)lementary key to species of Eeteromyia 360 TamipiiKC 361-398 Larval characters 362 Pupal characters 363 Imaginal characters 363 Key to genera (imagines) 361 Key to larva; 364 Key to pupa; 365 Unidentified larva3 397 Chironomina; 398-534 Key to genera 400 Key to larvaB 401 Key to pupa; 406 Unidentified larva; and pupa; 528-534 Distribution of CMronomidir in the Illinois Eiver 534 Summary of Illinois genera and species in comparison with those recorded for other states 530 Nundier of Illinois species recorded 536 Number of New Jersey species recorded 537 Number of species recorded by Johannsen 537 Index to genera and species 539 — Article VI. The Chironomida, or Midges, of Illinois, with particular Reference to the Species occurring in the Illinois River. By J. R. Malwch. Introduction The family Chironomidcc includes a very large number of species the adult forms of which, in the great majority of cases, are very difficult to distinguish from each other. The adults of the larger species of the genus Chironoinus and those genera closely related to it are often mistaken for mosquitoes, which they greatly resemble in general appearance. No adult of this group, Chironoiiiincc, nor of the Tanypi- n<T, has as yet been recorded as biting, and it is only in the Ccratopogo- nincc, the species of which are generally very much smaller and more robust, much less resembling the Ctdicidcc, that we meet with blood- sucking species. Some of the species in this latter group, known lo- cally as "punkies," are very persistent biters, and though of very small size occur sometimes in such numbers as to cause considerable incon- venience. This habit of some species in the Ccratopogonincc is not con- fined to those occurring in America. In Europe, particularly in the more northern parts, Cidicoidcs pidicaris Linne and several closely allied species are so numerous and bite so persistently in the evenings, during the months of June, July, and August, that it i.-' only by endur- ing much discomfort that one can remain outdoors in the country, or even on the outskirts of the towns in certain districts. This condition prevails in Britain, and is more pronounced in Scotland, especially near the many small lakes which exist, where conditions are almost unen- durable. Several species which attack man and cattle are dealt with in this papejr. The early stages of most species of this family are passed in water —rivers, lakes, pools, and streams, or in almost any receptacle contain- ing the requisite amount of water; but some species of the Ccratopo- gonincc are terrestrial in the larval stage, living underneath bark, under boards, or beneath other objects lying on the ground, while some of them are also met with in nests of Hymcnoptcra. A most peculiar form of larva belonging to this group and living on submerged logs, has been found by Garman in Kentucky*, and has also occurred in the •Bull. Ky. Agr. Exper. Sta., No. 159, p. 31, Figg. 27 and 28. 276 Illinois River at Havana. A detailed description of all stages of this species is given herein. The Chironomidcc, though resembling the Ctdicidcc in many respects, including the form of the adult and the aquatic habits of the larva;, do not present in the larval stage such characters as those which are so readily appreciable and so easily accessible in the larva; of the latter family. It is only in the terrestrial species of Ceratopogonina that one meets with conspicuously spinose forms, and in the great majority of cases a clue to the specific, and even generic, identity of a larva must be sought in the structure of the head and its parts, and also in the form of the anal appendages. The members of this family are among the commonest and most widely distributed of the two-winged flies, occurring on every conti- nent and in all the faunal areas into which these continents have been divided. Although considerably over one thousand species have been described, it is certain that this is but a small fraction of the total number of species which must occur throughout the world. The reasons for this paucity of described species are obvious. The fragile structure of most of the species prevents their being readily preserved, and their frequent close similarity deters all but a few specialists from working on the family. Despite the extremely fragile structure of the members of this family many fossil species have been described by various authors. Conjectures as to the possible sources from which the family sprang must remain, as in the case of other families, mere conjectures, serving only to create purely academic discussion, which has no proper place in the present paper. It may, however, be useful to students of the Diptcra to indicate, as clearly as possible from the available data, the characteristics of the family. In this paper I have introduced in descriptions of genera and species a few characters which have not previously been used by writers in dealing with the family. I have in every case endeavored to find coordinated characters in the sexes, and in dealing with the genera I have, wherever possible, associated the characters found in the adults with a certain set of characters found in larvae and pupae. I have, I believe, met with a considerable degree of success in deciding some of the more difficult points, particularly in the Ceratopogonina. The presence of the thoracic cavities in Cnlicoidcs and their absence from the members of closely allied genera serves as a much more satisfac- tory and more readily appreciable character for the separation of the genera than that previously in use, namely, the size of the empodia in comparison with the size of the claws. ' I have of course followed pre- vious authors in the main lines of separation, only occasionally deviat- ing when convinced that such course is expedient and conducive to a better understanding of the family; but in descriptions of species I 277 have used, wherever possible, such structural characters as were available in addition to those of color, even at the risk of being charged by superficial students with considering valueless ininuti?e as of specific importance. My duty to subsequent students of the group is, as I re- gard it, to avoid obscuring the distinctions between genera or species, and to place before them as clear a statement as I possibly can of the characters on which I depend for my identifications, thus enabling them to begin their work upon the family without the handicap which I had when I began—that of uncertainty as to the structural details of genera and species. METHODS OF COLLECTING Larv?e of Chirononiidcc may be met throughout the entire year in almost any permanent body of water, and often in temporary pools. Slow-flowing rivers and creeks and shallow lakes and ponds are both the most easily accessible and most productive of species. Earlv in March many species may be dredged from the beds of streams and ponds, and some of them, such as Protcnthcs adiciformis and Ortlwdadius nlvoriundns, may be obtained in large numbers in practi- cally any small stream. It is necessary in dredging for larvae that the mud or silt at the bottom should be disturbed to some depth, as most of the species burrow and must be dislodged before they can be obtained with the net. Provided, however, that the net is strong enough, quan- tities of mud may be lifted from the water and sifted over on some con- venient flat surface. The "blood-worms" are readily seen in the net, but most species are difficult to detect because of their brownish or grayish color, and it requires careful searching to find most of the species of Orthocladius and the smaller chironomine species. The wormlike larvae of Ccratopogonincc are also difficult to discover as they are almost colorless and exceptionally slender.

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