Envlronment Canada Environnement Canada Fisheries Service des pêches .1 and Marine Service et des sciences de la mer L .' 1 '; ( 1 l r A Guide for the Identification of Two Subfamil ies of Larval Chironomidae: ,1"'--- The Chironominae and Tanypodlnae . : - - . ) / Found .in Benthic Studies Jin the / r~---.-_ c L___ r - - '" - .Ç"'''''-. Winnipeg River in the Vicinity ot Pine Falls, Manitoba in 1971 and 1972 by P. L. Stewart J.S. Loch Technical Report Series No. CEN/T-73-12 Resource Management Branch Central Region DEPARTMÈNT OF THE ENViRONMENT FISHERIES AND MARINE SERViCE Fisheries Operations Directorate Central Region Technical Reports Series No. CEN/T-73-12 A guide for the identification of two subfami lies of larva l Chironomidae~ the Chironominae and Tanypodinae found in benthic studies in the Winnipeg Riv~r in the vicinity of Pine Falls, Manitoba, in 1971 and 1972. by: P.L. Stewart qnd J.S. Loch ERRATA Page13: The caption for Figure 5A should read: Mentum and ventromental plates..•... instead of: submentum and ventromental plates..•.. Page 14: The caption for Figure 5B should read: Mentum and ventromental plates . instead of: submentum and ventromental plates.... DEPARTMENT OF THE ENVIRONMENT FISHERIES AND MARINE SERVICE Fisheries Operations Directorate Central Region Technical Report Series No: CEN/T-73-12 A GUIDE FOR THE IDENTIFICATION OF IWO SUBF.AMILIES OF LARVM.... CHIRONOMIDAE: THE CHIRONOMINAE AND TANYPODINAE FOUND IN BENTHIC STUDIES IN THE WINNIPEG RIVER IN THE vrCINITY OF PINE FM....LS, MANITOBA IN 1971 and 1972 by P. L. Stewart and J. S. Loch Resource Management Branch Fisheries Operations Directorate Central Region, Winnipeg November 1973 i ABSTRACT Identifying characteristics of the genera of two subfamilies of larvae of the midge family, C~onomldae (Vlpt~a), the C~ono­ mlnae and the Tanypodlnae, are presented with illustrations for the purpose of simplifying identification of these two groups by novice and more experienced personnel involved in assessment of benthic faunal composition. ii ACKNOWLEDGMENTS O. Saether, A~ Hamilton and W. Warwick of the Freshwater Institute (Winnipeg, Manitoba) verified identification of sorne of the specimens used in this guide. o. Saether read and criticized the manuscript. W. Warwick gave advice on nomenclature and helped clarify obscure differences between sorne genera. Many of the photographs and illustrations were taken from specimen slides in the Freshwater Institute collection. iii TABLE OF CONTENTS Page Abstract ••••••• ............................................................................ III . i AcknowLedgments .. ii List of Figures .. iv Introduction .. 1 Notes on use of guide •••••••••••••••.•••.•••••••••••.•• 3 Note on terminology used ••••••••••••••••••••••••••••.••• 5 Subfamily Characteristics ••.•••• 6 Generic Characteristics ••••••••••••••••••••••••••••.•••••• 17 Refererices D ' .. 46 iv LIST OF FIGURES Page Fig. 1 Head capsule characteristics of Chironomus 9 Fig. 2 Antennal types found in larvae of t~e tribe Chironomini ...•...•.•.•.•.•.•.......•............... 10 Fig. 3 Head capsule characteristics of Micropsectra Il Fig. 4 Head capsule characteristics of Procladius 12 Fig. 5 Mentum and ventromental plates of larval Chironomini ;................. 13, 14 Fig. 6 Antennae and mental structures of several Tanytarsini ',' ~ ...•...... Il •••• " 15 Fig. 7 Lf.guLa and pavaglossa of the larvae of several Tanypodinae .•...•.•..•..•.•.•.•.•.•...•.•.•......... 16 Fig. 8 Chironomus-larval head capsule characters 20 Fig. 9 Glyptotendipes-larval head capsule ~haracters 21 Fig. 10 Dicrotendipes-larval head capsule characters 22 Fig. 11 Polypedilum (Pentapedilum)-larval head capsule 'chat-acters ....•.•..•.•.....•........................ 23 Fig. 12 Polypedilum (Fallax)-larval head capsule characters ............•..•....•..................... 24 Fig. 13 Microtendipes-larval head capsule characters 25 Fig. 14 Paratendipes-larval head capsule characters 26 Fig. 15 Cryptochironomus-larval head capsule characters ..... 27 Fig. 16 Demicryptochironomus-larval head capsule characters. 28 Fig. 17 Head capsule characters of Endochironomus, Phaenopsectra (Phaenopsectra) and Phaenopsectra (Tribelos) ...•.... 30 Fig. 18 Endochironomus-larval head capsule characters 31 v Page Fig. 19 Stictochironomus-1arva1 head capsule characters..... 32 Fig. 20 Parac1adopelma-1arval head capsule characters....... 33 Fig. 21 CpYptotendipes-1arval head capsule characters....... 34 Fig. 22 Cryptocladope1ma-larval head capsule charactets..... 35 Fig. 23 Micropsectra-1arval head capsule characters.,........ 36 Fig. 24 Tanytarsus-larval head capsule characters........... 37 Fig. 25 Stenochironomus-larval head capsule characters...... 38 Fig. 26 Parachironomus-larval head capsule characters....... 39 Fig. 27 Ablabesmyia-larval head capsule characters.......... 40 Fig. 28 Larval head capsule characters of Coelotanypus and Clinotanypus....................... 41 Fig. 29 Thienemannemyia group -larval head capsule characters ".. 0 • • • • • • • • • 42 Fig. 30 Procladius-larval head capsule characters........... 43 Fig. 31 Tanypus-larva1 head capsule characters.............. 44 Fj,g. 32 Psectrotanypus-larval head capsule characters....... 45 l INTRODUCTION Larval Chironomidae (Diptera) are one of the more important groups of organisms to be encountered in most benthic studies. The' group has a cosmopolitan occurrence, occupying a wide range of benthic habitat, in streams, lakes, pools, estuaries, and subject toa variety of environmental conditions. In addition, the Chironomids make a significant contribution to the biomass and nûmbers in benthic communities and can probably be considered the most frequently encountered inverte­ brates in fresh water studies. The plasticity of the Chironomidae as a group in their range of habitat is reflected in the diversity of .fo rm found in the group. The Chironomidae encompasses more genera and more species than any other insect group -- new species are discovered almostas fast as unexplored geographical areas are opened to the Chironomid taxonomist. Recent interest in benthic studies in assessing the effects of man on his aquatic environment (pollution, construction and mechanical effects, eutrophication etc. in lakes and streams) has led to a need for a more precise assessment of benthic systems in terms of what organisms are contained in them and how the organisms will react ta environmental changes caused by man. The predominance of Chironomidae in freshwater benthic systems makes them an ideal and important group ta deal with inthis regard. In such studies, identification of larval Chironomidae ta at least the generic level is almoqt certainly involved. This may pose problems since accurate identification may involve as much or more time and effort as the interpretive effort, and often requires considerable 2 familiarity with the literature dealing with Chironomid taxonomy. The purpose of this report is ta assist in the identification of sorne larval Chironomids. It is designed primarily ta help persans starting out in Chironomid identification, but also ta act as a reference for persons with more experience. Included are the useful generic characters of two Chironomid subfamilies, the Chironominae and the Tanypodinae. There are four additional subfaII)ilies (Orthocladiinae, Podonominae, Telmatogetoninae and Diarnesinae) which form a significant part of the Chironomidae but which are not dealt with here. Hopefully identification experience gained with these two subfamilies will facilitate reference work on the other subfamilies. Illustrations for the guide were taken largely from samples taken in Fisheries Service benthic studies on the Winnipeg River in the '11, summers of 1971 and 1972. Illustrations of additional genera were taken from specimen slides in the Fisheries Research Board, Freshwater Institute (Winnipeg, Manitoba) collection. Host genera in the subfamily Chironominae are included in the guide, although not aIl are illustrated. The subfamily Tanypodinae is not as weIl represented but aIl cornmon genera are included. Most of the characteristics presented her~ have been taken from available literature sources and from a provisional key by Hamilton and Saether at the Freshwater Institute in Winnipeg. Additional characteristics came from persona.l communication with A. Hamilton, O. Saetherand W. Warwick at the Freshwater Institute. The characteri- stics presented were felt ta be the most useful in identification of specimens of the level of preparation likely ta be encountered in an average benthic operation. 3 NOTES ON USE OF GUIDE The guide is divided into two sections, one dealing with subfamily and tribe characters, the other with generic characters. The section on subfamily and tribe characters contains a description of the subfamilies Chironominae and Tanypodinae, and of the two tribes of the Chironominae, the Chironomini and Tanytarsini. This description is followed by several figures (Figures 1 - 4) illustrating the subfamily and tribe differences. In addition, Figures 5 - 7 give an overview of important features in genera of the two subfamilies. The most useful approach 'in using the guide is to become familiar with the subfamilyand tribe characters by way of the illustra­ tions (Figures 1 - 4), while referring to the particular specimen to be identified. Figures 5 - 7 then provide a rapid means of finding a genus which is at least similar to the one being examined. The section on generic characters contains illustrations and accounts of the