Chironomini (Diptera: Chironomidae: Chironominae) Keys to Central European larvae using mainly macroscopic characters Second, revised edition Claus Orendt Martin Spies sponsored by Deutsche Gesellschaft für Limnologie e.V. Preface to the second edition 3 The original, German-language edition of ture as recent as feasible that offers possi- this work, Orendt & Spies (2010), met bilities for further identification. Readers with such demand that it sold out soon should be aware, however, that the applica- after its publication. Continued interest, tion of such references may require more not least from outside of Germany, has involved working methods and/or greater encouraged us to produce a second edi- experience. tion, this time in English. Besides translation of the German ver- The authors would be glad to see this ver- sion, the present work also offers a num- sion of the Chironomini key find the same ber of changes in content that are aimed reception as the first edition, and will be at making some parts of the keys even most grateful for any feedback to help us easier to use. Such modifications concern improve this taxonomic tool. • early keying of taxa that can be rec- ognised readily by head capsule pat- Lastly, we would like to announce in ad- tern or body shape; vance a comparable work that is scheduled • improvements to some illustrations, to become available in autumn of 2012 (see and addition of new ones; also last page). Orendt et al. (in press) will • the incorporation of Glyptotendipes present keys to all chironomid taxa that are ospeli , which has been recorded re- identifiable in the larval stage and are known peatedly from Central European low- to occur in brackish waters of German and land waters. adjacent North Sea and Baltic Sea coasts. These items have necessitated the re- The book will be available in separate Eng- structuring of some taxon sequences in lish and German editions. the key. However, none of these changes have made the first edition significantly less applicable. Leipzig and Munich, August 2012 A number of readers have asked whether some taxa could be made identifiable at lower ranks of the systematic hierarchy than in the first edition. We should like to honour these requests while remaining true to the general design of this work specifically for users who are relatively inexperienced with chironomid larvae. Therefore, several corresponding termi- nals in our key now refer to special litera- 4 Introduction In Central European standing waters, the ductivity, functional processes or any other larvae of Chironomini constitute a most important aspect. important part of the chironomid fauna. The present authors are hoping to remove The group includes a major share of what such barriers and reservations against chiro- is commonly known as 'red midge larvae' nomid determinations by offering a key that or 'bloodworms', since the larvae of most mainly uses 'macroscopic' morphological Chironomini species carry molecules in features discernible at relatively low magni- their body fluids that bind oxygen and fication, while it resorts to microscopic char- cause colouration in similar fashion as acters only where this is unavoidable. Our human hemoglobin. For the same reason approach aims to facilitate successful identi- some species are capable of producing fications especially by workers who have enormous numbers and densities of indi- little previous experience with midge larvae. viduals especially in nutrient-rich or pol- Another beneficial consequence could be lutant-laden waters. As a result, both the that more studies will begin to unlock the aquatic immature stages and the aerial critical ecological information that is often adults of these midges often attract the wasted when the chironomids present in a attention of water engineers and manag- habitat are left undetermined, whereas ers, as well as of members of the general fewer studies will stop at meaningless com- public, even those otherwise little inter- parisons of 'Chironomidae indet.' or the like ested in natural phenomena. with other taxa identified at genus or species In the family Chironomidae the animals level. are so small that they cannot be studied Naturally, as in any group of organisms, reli- with unaided eyes, the species diversity is able identifications of non-biting midge lar- very high, and the literature one has to vae in many cases will be reached only as consult for detailed identifications often the result of intensive study and experience, amounts to numerous specialised works including attention to the specialist scientific rather than just a few comprehensive literature. However, the present work has ones. These and other factors have com- been designed to open a gate and get the bined to give the group a reputation of reader started in that direction. requiring relatively high effort for deter- The keys offered below separate the Central minations and interpretations. For these European Chironomidae larvae by subfami- reasons many macroinvertebrate workers lies, and then the members of the tribe Chi- have stayed away from adequate consid- ronomini in the subfamily Chironominae. eration of non-biting midges, even With many Chironomini, no special prepara- though they do not dispute the group's tions of the material will be necessary for significance in the studied ecosystems identifications to genera, occasionally not concerning faunal diversity, biomass pro- even for species. Glossary 8 Body Thorax Abdomen 3 segments 9 segments Posterior abdomen Lateral tubules Ventral tubules Lateral tubules Without tubules anterior posterior Parapods (false feet) A1: Subfamilies 12 Eyespots Ventromental plates ( ) usually 2 and well separated along a vertical or slightly usually relatively wide and distinct (occasionally rather transparent); oblique line; with or without distinct beard setae in some cases the lower eyespot is subdivided, in others the upper and lower spots are almost fused Chironominae beard Prodiamesinae A2 Faasch (orig.) 1 or 2; in some cases in an almost horizontal line; or usually absent or indistinct and relatively narrow; eyespots absent beard setae absent or very rarely distinct Orthocladiinae Diamesinae Podonominae Tanypodinae Buchonomyiinae Telmatogetoninae A4 Orthocladiinae Tanypodinae B1-4: Chironominae: Chironomini 19 Abdomen 8th segment Chironomus with 2 pairs of sp. ventral tubules (some species) for identification of certain species, see Vallenduuk et al. (1995), Vallenduuk & Langton (2010), Orendt & Spies (2012) Photo: Faasch 8th segment with 1 pair of long or short ventral tubules B1-5 Photo: Janecek Photo: Faasch 8th segment without ventral tubules B1-9 B1-7: Chironominae: Chironomini 22 with 1 pair of ventral tubules Head / Posterior abdomen Head in dorsal view ( ) Ventromental plates and mentum head long central ventromental plates touching medially, one plate as sclerite > 2 x as wide as the mentum; mentum with a group of 4 long relatively central teeth (appearing as a single tooth when worn; see as wide , p. 47) that are slightly shorter than the 1st lateral teeth wide the unpaired sclerite anterior to it indistinct; modified long sclerite with medial from Kiknadze ventral et al. (1991) Lipiniella tubules longitudinal furrow, anterior moderata short to that a granulated depression , farther anterior the surface is smooth (examine also from the side) head longer than modified from wide Kiknadze et al. (1991) long central sclerite ventromental plates separated by distinct medial gap, tapering to a point one plate not wider than the mentum; posteriorly , without longitudinal furrow, Benthalia ventral the unpaired sclerite carbonaria tubules anterior to it distinct; central tooth of short long sclerite mentum larger than ('dissidens' anteriorly without any lateral tooth eco-variety) Photo: depression , smooth Faasch B3-1: Chironominae: Chironomini 41 without ventral tubules - mentum with 1 central tooth Head above the mouth opening ( ) Mentum ( ) Mandible labrum with a brush of long chaetae entirely and uniformly dark; central inner teeth barely discernible or that is retractable/eversible, thus and 1st lateral teeth surpassed by the absent varies in extension among specimens 2nd laterals (even the apical tooth can be worn down to a short stump) Xenochironomus xenolabis Photo: Faasch ! often strongly worn, so that the anterior margin looks different: in freshwater sponges Photo: Faasch labrum without brush with at least a few teeth always inner teeth usually discernible; in some taxa, certain teeth discernible, if low are darker than others; and flat-tipped ( ) see illustrations on p. 44 (B3-4) then apical tooth with +/- acute tip B3-2 B3-9: Chironominae: Chironomini 49 without ventral tubules - mentum with 1 central tooth Head Mentum wider posteriorly anterior margin nearly straight or slightly convex , teeth not always clearly distinguishable; central tooth wide, with or without notch; in some cases the tips of some lateral teeth point diagonally to medial rather than straight ahead B3-10 wider posteriorly anterior margin distinctly convex in most cases; where it is nearly straight, the teeth are clearly or oval distinguishable; central tooth with or ( ) without medial notch; tips of lateral teeth usually pointing straight ahead B3-11 notch notch B3-12: Chironominae: Chironomini 52 without ventral tubules - mentum with 1 central tooth Head: pattern Mentum ventrally with a brown area interrupted central tooth not distinctly projecting to anterior, frequently with medial notch by