Atlas of Larvae of the Chironomid Midges (Class Insecta: Order Diptera: Family Chironomidae) Recorded at the Old Woman Creek National Estuarine Research Reserve and State Nature Preserve, Ohio by Natalie J. Johnson, Tamara S. Keller, and Kenneth A. Krieger National Center for Water Quality Research Heidelberg College Tiffin, Ohio, USA 44883 First Revision July 2007 Atlas of Larvae of the Chironomid Midges (Class Insecta: Order Diptera: Family Chironomidae) Recorded at the Old Woman Creek National Estuarine Research Reserve and State Nature Preserve, Ohio Acknowledgments The authors are grateful for the assistance of Dr. David Klarer, Old Woman Creek National Estuarine Research Reserve, for providing funding for this project and for his critical reviews of drafts. This work was funded under contract to Heidelberg College by the Ohio Department of Natural Resources, Division of Natural Areas and Preserves. We also thank Mr. Mike Bolton, Ohio EPA, Division of Surface Water, Ecological Assessment Section, for critically reviewing the first version of this chapter, suggesting improvements in its scientific accuracy, and for providing specimens of the genera added to this revision. “This publication was supported [in part] by Grant Number H50/CCH524266 from the Centers for Disease Control and Prevention. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of Centers for Disease Control and Prevention.” “The Old Woman Creek National Estuarine Research Reserve in Ohio is part of the National Estuarine Research Reserve System (NERRS), established by Section 315 of the Coastal Zone Management Act, as amended. Additional information about the system can be obtained from the Estuarine Reserves Division, Office of Ocean and Coastal Resource Management, National Oceanic and Atmospheric Administration, U.S. Department of Commerce, 1305 East West Highway – N/ORM5, Silver Spring, MD 20910. Financial support for this publication was provided by a grant under the Federal Coastal Zone Management Act, administered by the Office of Ocean and Coastal Resource Management, National Oceanic and Atmospheric Administration, Silver Spring, MD.” Copies of this publication are available from the Ohio Department of Natural Resources-Division of Wildlife 2514 Cleveland Road East Huron, Ohio 44839 This publication can be downloaded at www.heidelberg.edu/wql/educationoutreach/reports. Introduction Both the formal biologist and the amateur naturalist often encounter lists of animals and plants when they visit nature centers and read published scientific reports. Rarely can they readily access drawings or photographs of each member of the list so that they can distinguish one from the other. The purpose of this atlas is to provide a detailed pictorial record of one group of organisms – the midges, a kind of true fly (Order Diptera) comprising the Family Chironomidae – within the Old Adult male midge (chironomid). Scale is in Woman Creek coastal wetland system centimeters. Photo: David J. Dariano (OWC) along Lake Erie in Ohio. Invertebrates occur in great abundance the correct identification of the midge in freshwater ecosystems, including larvae found as of 2007 at OWC to the Great Lakes wetlands such as the level of genus. Visualization of many of marshes and swamps that make up the features requires “clearing” of OWC. A few of those invertebrates, specimens (making them mostly such as freshwater mussels, grass transparent). Detailed processing shrimps, and giant water bugs, are methods are described in several of the readily visible because of their large size. references listed below. Many freshwater invertebrates, however, are so small that special attention must The midges are a very diverse group be given to collecting – and seeing – comprised of thousands of species them. Thus, most groups of worldwide. The nonbiting winged adults invertebrates go unnoticed by casual form highly visible mating swarms and visitors to aquatic habitats. Larval can create a harmless nuisance as they midges of the Family Chironomidae are rest in large numbers on objects (and no exception. They range in length from people). Because of their great less than 1 mm to more than 2 abundance, both larval and adult centimeters. Once collected, the ability midges provide an important food to distinguish one kind of midge from resource for aquatic predators such as another requires careful observation of fishes, and terrestrial predators ranging minute structures through a compound from dragonflies to songbirds. Midge microscope at magnifications as high as larvae are adapted to a variety of 400X or even 1000X. different aquatic habitats and ecological conditions; therefore, the kinds of midge This atlas constitutes one of several larvae found in a stream, lake, or chapters that will comprise a wetland can reveal information about comprehensive atlas of the biota of the the quality, or “health”, of the OWC wetland system. This particular ecosystem. chapter presents detailed photographs of critical diagnostic features that permit Characteristics of Larval Chironomidae Ab As members of the insect Order Diptera, midges have four life stages: egg, larva, pupa, and adult. In most species, all T stages except the adult are aquatic, and VT the larval stage is the one most often H found in samples taken from aquatic PP AP habitats. The larva has four intervals, or AT instars, between hatching from the egg 0.5 mm and becoming a pupa, shedding its exoskeleton (molting) at the end of each Chironomid (Chironominae) larva instar. The largest, fourth instar is the most reliable stage for observing the distinguishing features of the different genera and species. Nevertheless, many times only earlier instars are T available for identification. H General features of a midge larva are An shown in the photographs on this page. The body is divided into three regions: head (H), thorax (T) consisting of three Md segments, and abdomen (Ab). The Mt entire outer covering of the head consists AP of a hardened (sclerotized) head capsule with numerous specialized structures useful for identification. Head Anterior end of Chironomus sp. structures include, among others, a pair of antennae (An), a pair of mandibles (Md), and a mouth part called the mentum (Mt). Midge larvae lack true Ab legs but do have a pair of anterior prolegs, or parapods (AP), that extend ventrally beneath the head and a pair of posterior prolegs, or parapods (PP), extending from the last abdominal segment. The last segment also typically Pr VT bears a pair of fleshy procerci (Pr) tipped with numerous hair-like setae, and PP two pairs of anal tubules (AT). The AT genera Kiefferulus and Chironomus have one pair or two pairs,respectively, of Posterior end of Chironomus sp. ventral tubules (VT) near the end of the abdomen. Layout of this Atlas general ecology of the genus is briefly summarized, including its habit (such as The following pages are organized sprawler, tube builder, or burrower), its alphabetically by subfamily. Biologists functional feeding group (such as have identified twenty-six genera of shredder, collector, or predator), and for chironomids in three subfamilies some genera, special notes about their (Chironominae, Orthocladiinae, and habitat or water quality requirements. Tanypodinae) in samples collected since the 1980s from numerous habitats within All information on each page was derived the OWC wetland system. from three or more references, 0.1which mm are abbreviated as shown below followed by This publication should not be used as the page number(s): the sole source to identify the genera of larval chironomids of OWC because it is E = Epler, J.H. 2001. Identification likely that additional genera will be found manual for the larval Chironomidae in new collections. The references cited (Diptera) of North and South Carolina. below should be used to obtain definitive Version 1.0. identifications. The species within each http://www.esb.enr.state.nc.us/BAUwww/ genus are not addressed here and the Chironomid.htm. species of some genera cannot be identified. C&F0.1 mm= Coffman, W.P., and L.C. Ferrington, Jr. 1996. Chapter 26. Each genus of midge larva is illustrated Chironomidae, pp. 635-754. In: Merritt, and described on a single page of this R.W., and K.W. Cummins (Eds.). An atlas. Because the identifying features introduction to the aquatic insects of of the Family Chironomidae and the North America. 3rd Ed. Kendall/Hunt particular subfamily are repeated on Publ. Co., Dubuque, Iowa. each page, the page for each genus can be used independently. Photographs R = Roback, S. S. 1957. The immature are labeled with lines that point to tendipedids of the Philadelphia area. diagnostic structures. Most Monographs of The Academy of Natural photographs are of specimens collected Sciences, No. 9. George W. Carpenter within OWC, and the exact specimens Fund Printing, Philadelphia, photographed are recorded at the Pennsylvania. bottom of the page. Details in many photographs can be seen more clearly S&B = Simpson, K.W., and R.W. Bode. when enlarged on a computer screen 1980. Common larvae of Chironomidae than when printed on paper. (Diptera) from New York State streams and rivers with particular reference to the Beneath the descriptive features, each fauna of artificial substrates. Bull. No. page lists where within OWC the genus 439, New York State Museum, Univ. of has been found (its habitat). It is likely the State of New York, State Education that future collections will