Trichoptera Larvae of Finland 3 Trichoptera Larvae of Finland TRICHOPTERA LARVAE OF FINLAND © ALL RIGHTS RESERVED AKI RINNE PETER WIBERG-LARSEN IDENTIFICATION KEY TO THE CADDIS LARVAE OF FINLAND AND NEARBY COUNTRIES Contents 4 Trichoptera Larvae of Finland CONTENTS Preface 5 Limnephilidae 68 Acknowledgements 6 Main key 69 Introduction 6 Sub-key A 70 Biodiversity, biology & ecology 8 Sub-key B 77 Trichoptera of Finland 12 Sub-key C 78 Regional Biodiversity 12 Sub-key D 82 Collection, preservation and examination 14 Sub-key E 86 Classification 16 Sub-key F 93 Morphology 18 Limnephilidae - Character tables 100 Keys and identification 22 Molannidae 104 If identification fails 23 Beraeidae 106 Nomenclature 23 Sericostomatidae 108 Separation of instars 24 Odontoceridae 108 Key to families 28 Leptoceridae 109 Contents Rhyacophilidae 35 Biogeographical provinces 122 Glossosomatidae 36 Distribution maps 129 Hydroptilidae 38 References 148 Philopotamidae 41 Index 150 Psychomyiidae 42 Ecnomidae 43 Polycentropodidae 44 Arctopsychidae 47 Hydropsychidae 47 Phryganeidae 51 Lepidostomatidae 58 Brachycentridae 59 Goeridae 60 Apataniidae 62 Apataniidae - Pictorial key 66 Trichoptera Larvae of Finland 5 Preface PREFACE This is the first comprehensive key for identification of larvae of the Trichoptera species inhabiting northern Europe. Until now, identification of Trichoptera specimens sampled within this area has relied on the key to genera published by Solem & Gullefors (1996), supplemented with the key to species from the British Isles (Wallace et al. 2003), and on publications describing only specific species or presenting keys to single families or genera (e.g. Solem 1970, 1971, 1972, 1981, 1983, 1985; Wiberg-Larsen 1979, 1980; Wiberg-Larsen & Waringer 1998). The relative scarcity of taxonomic literature on Trichoptera in northern Europe is somewhat surprising given the rather inten- sive interest from both amateurs and professionals during the last century, for instance A.J. Silfvenius/Siltala, O. Nybom (Finland), P. Esben-Pedersen, A. Nielsen, P. Wiberg-Larsen (Denmark), T. Andersen, J.O. Solem (Norway), G.M. Gislasson (Iceland), and B. Tjeder, B.W. Svensson, and B. Gullefors (Sweden). Providing a key like this for Finland and its neighbouring However, recent barcoding techniques (using nuclei acid sequence countries has been a challenging task, requiring more than ten analyses on mitochondrial DNA) have provided an important years of work involving field trips to collect material, microscopy, breakthrough in the work on Trichoptera identification, rendering drawing or photographing details and, not least, constructing association of adults with their larvae more reliable and easier. and testing the keys. Not only is the number of species relatively Despite this technical progress and sample efforts, the larvae of high, about 240 species being recorded in Finland and its about 30 species (mostly Hydroptilidae) are still unknown or neighbouring countries, but the book also includes 17 species insufficiently described and therefore not included in the present for which the larvae have been unknown and several others keys for identification. hitherto only insufficiently described. Historically, association of Preface larvae with their corresponding adults has relied on either rearing With this book we hope to make the biodiversity and fascinating from larvae to pupae and adult or from eggs to mature larvae, a life of Trichoptera larvae available to all – professionals as well as process that is both time-consuming and technically challenging. amateurs – with interest in our fresh and brackish waters. Aki Rinne. Peter Wiberg-Larsen. Aquatic Insects Expert Group of Finland. Institute for Bioscience, Aarhus University, Denmark. Address: Merikasarminkatu 8 D 53, 00160 Helsinki, Finland. Address: Vejlsøvej 25, DK-8600 Silkeborg, Denmark. E-mail: [email protected] E-mail: [email protected] Biodiversity, biology & ecology 8 Trichoptera Larvae of Finland BIODIVERSITY, BIOLOGY & ECOLOGY World-wide, more than 14,500 species of Trichoptera belon- Trichoptera are an important element in the biological structure ging to 616 genera and 49 families are listed in the “Trichoptera of stagnant and running waters. In North-Europe, they belong World Checklist” (by September 2016). Although on a global to the top three, most species-rich animal groups, only being out- scale, Trichoptera is one of the smaller insect orders compared numbered by Chironomidae in streams and rivers and by Chiro- with the big four orders (Coleoptera, Diptera, Lepidoptera and nomidae and Coleoptera in pools, ponds and lakes. Not only do Hymenoptera) and only just qualifies to be in the “top ten”, they the larvae process dead or live organic matter, they also serve as are very prominent in freshwater bodies. Thus, world-wide, the food for top predators like dragonflies, amphibians, several fish order is more species-rich than other insect orders and arthropods species and a suite of birds, ranging from the dipper, grey wagtail, in the freshwater environment. waders to grebes and ducks. Furthermore, their adult stages enter the terrestrial food webs where they act as prey for, for instance, In the Palearctic region (which includes Europe), there are mo- spiders, predaceous beetles, numerous birds and bats. re than 1500 species, belonging to 149 genera and 23 families. However, the species number decreases considerably towards the Constructions north to approx. 15% of the European fauna (Wiberg-Larsen 2005). At present, 218 Trichoptera species have been identified Trichoptera are probably best recognised by nature-interested in Finland. Compared with the adjacent countries, this number persons by their portable cases that are constructed from different is slightly lower than in Sweden where 224 species have been materials such as fine gravel, sand, fresh or dead pieces of plant recorded so far (Gullefors 2015), but higher than in Norway (201 materials or of silky material only. Furthermore, the larvae have species: Kjærstad et al. 2010, Andersen & Hagenlund 2012, Ek- traditionally been classified as either case-bearing or free-living, rem et al. 2012) and Estonia (190 species: Viidalepp et al. 2011). although this is not a correct interpretation. Actually, only one The number of species in northern Europe are shown at the map family (Rhyacophilidae) includes truly free-living species that below (data for Russian areas based on Ivanov (2011)). only construct a case of coarse mineral particles fixed to a stone when the larva is about to pupate. All other families without Overall, the number of Trichoptera species is expected to increase portable cases build either retreats on macrophytes, stones or logs with the size of a water body. This has been nicely documented for (associated with capture nets – see below), or long tubes of fine near-pristine lowland Danish streams ranging from tiny brooks to mineral or organic particles that are fixed firmly to stones or logs. small rivers (Wiberg-Larsen et al. 2000). The same pattern applies to the continuum of standing waters from the tiniest pools to the The ecological success of Trichoptera seems to be closely associated largest lakes. There are at least two reasons for this pattern that with their ability to produce strong silky treads that are used either may also be observed for other groups of organisms. First of all, to glue together case material or produce nets for filtering fine large water bodies may hold a larger number of individuals than organic particles or capturing prey. As for Lepidoptera, the silk small ones, which augments the chances of occurrence of more is produced by labial glands composed of a few tens or hundreds species. Furthermore, large-sized water bodies may contain more of large polyploid cells secreting polymerising proteins that Biodiversity, biology & ecology Biodiversity, habitats than small ones, thereby offering favourable life condi- are stored in the gland lumen as a semi-liquid gel (Sehnal & tions for more species. Sutherland 2008). The conversion (polymerisation) of this gel into NW-Palearctic region Svalbard (1) Kola peninsula (108) Iceland(12) Arkhangelsk Karelia region region Sweden (188) (224) Finland (218) Palearctic region Norway (201) St. Petersburg region (177) >1500 species Estonia (190) European Russia (235) Trichoptera Larvae of Finland 9 Biodiversity, biology & ecology Rhyacophilidae Glossosomatidae Hydroptilidae Philopotamidae Arctopsychidae & Hydropsychidae Psychomyiidae Polycentropodidae Biodiversity, biology & ecology Biodiversity, Brachycentridae Lepidostomatidae Goeridae Molannidae Odontoceridae Phryganeidae Leptoceridae Beraeidae Sericostomatidae Apataniidae Limnephilidae Trichoptera of Finland 12 Trichoptera Larvae of Finland TRICHOPTERA OF FINLAND REGIONAL BIODIVERSITY At present, a total of 218 Trichoptera species, belonging to 76 The climate in Finland is overall continental but shows the cha- genera and 19 families, are recorded in Finland. A detailed racteristics of maritime influence when westerly winds prevail. checklist is presented on pages 123-129, including occurrences The climate is therefore considerably milder than in areas situated in the 21 Finnish provinces. This checklist also includes the recent at similar latitudes (e.g. South Greenland and Siberia). Due to the assessment of their national conservational status, the so-called north-south orientation and size of the country, the temperature red-listing. regime differs widely between its regions, the mean differences