The study of Orthocentrinae s. l. (Hymenoptera, Ichneumonidae) in Eastern Fennoscandia Andrei Humala Forest Research Institute, Karelian Research Centre, Russian Academy of Sciences, Pushkinskaya 11. Petrozavodsk 185610, Karelia, Russia. [email protected] Introduction The biological diversity in a very significant degree depends on insect species diversi- ty, as insects is one of the richest in species class of living organisms. Among them hymenopterous insects, and especially parasitic Hymenoptera occupy one of the first places. For instance, according to the modern data, there are more than 6000 known species of these insects occurring in Finland (Koponen et al. 1995). As a result, its fauna is not satisfactorily studied. This group is characterized by an exceptional species diversity, surpassing other groups of insects. Taxonomy of the family Ichneumonidae is for the present day poorly developed in comparison with other groups of insects (e.g. Lepidoptera or Coleopte- ra). Occupying the highest level in food chains, ichneumon-flies thus represent one of the vulnerable groups of organisms. The subject of my research is the fauna of Orthocentrinae, one of the least-studied subfamilies of ichneumon wasps. For a long time the species composition of this group and its position within the family Ichneumonidae were obscure. It is necessary to note that this group of ichneumon-flies is of significant theoretical interest, as it occupies a key position for the solving of some difficult questions in Ichneumonidae phylogeny. Orthocentrines are small, seldom medium-sized parasitic wasps. The average size of its body is about 3-5 mm. The diversity of morphological structure of Orthocentri- nae is very significant. The present study was mainly restricted to the Microleptinae Townes = Oxytorinae van Rossem = Helictinae (Dasch 1992). These ichneumon-flies are extremely various in habitus. Thus different genera were considered earlier in diffe- rent subfamilies. Even the subfamily name is unstable and has changed several times during last 30 years. It has traditionally been known by the name Microleptinae. Henry Townes – the best specialist in Ichneumonidae of our time, who devoted whole his life to its study, called this subfamily a “waste-basket” group (Townes 1971). The majority of specialists in this field of study consider now the group inside Orthocentrinae s. l. (Wahl 1986, Wahl & Gauld 1998). New views have persisted for the last 15 years and have been generally applied (Yu & Horstmann 1997). Until the beginning of XX century, when Walther Hellén started his Ichneumoni- dae study, the data on Eastern Fennoscandian fauna of this group was extremely scant. In a set of articles he observed Finnish fauna of ichneumonids and reported many species new for Finland. Since 1960s Reijo Jussila has began the study of Finnish Ichneumonidae, and cove- red many groups of this family. Based on van Rossem (1980) who revised the West Palaearctic fauna, he reported many species as new for the Finnish fauna and described two new species of Orthocentrinae as well (Jussila 1994). Karelian fauna of this subfa- mily was practically unstudied until the end of 1980s. ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ The Finnish Environment 485 ○○○○○○○○○○○ 193 Materials and methods For the present study extensive collections have been made in Karelia (Fig. 1), especially in nature reserves Kivach and Kostomukshski, National parks Vodlozerski and Paanajärvi, planned Kale- vala National Park, biosphere reserve “Northern Karelia” and Kizhi skerries. Concerning other are- as, as a rule briefly visited, only small and occa- sional samples were available. Malaise traps, win- dow traps of different modifications, light traps as well as sweep netting and rearing from mush- room fruit bodies were applied for the original materials collecting. Additional materials for the study were obtained from the collections of the Zoological Museum of Helsinki University and collections stored at the Department of Applied Zoology of Helsinki University, which I could stu- dy in 1996 and in 1998. Available collections of the Zoological Museum (St.Petersburg) from Eas- tern Fennoscandia were treated as well. The study of insects associated with various ecological groups of mushrooms has been con- ducted at the Forest Research Institute of Kareli- an Centre of Russian Academy of Sciences du- ring many years. Mycetophagous insects, their predators and parasites, as was found out in our researches, are very diverse and numerous in bo- real forests. At the present, the structure of Dip- tera and Coleoptera communities associated with Fig. 1 Collecting areas: large dots - places where mushrooms is rather well investigated. But not extensive collections were made. small dots - less various and numerous complex of their para- places where only small and occasional samples sites until now practically was not investigated. were collected Such data in the world literature are extremely scant, and the species-rich group of ichneumon- flies, as Orthocentrinae, parasitizing on larvae of fungus gnats, was almost not studied. Very little was known about the biology of the group, but some species indicated as koinobiont endoparasitoids of the Mycetophili- dae larvae (Wahl 1986). Results and discussion Special study aimed to make up for the deficiency of knowledge and to clarify the host preference of Orthocentrinae was performed in Karelia. Reliable data on the hosts preference were received by rearing from mushrooms fruit bodies. 21 species of ichneu- mon-flies, which are considered as the parasitoids of dipterous mycetobiontes, were reared from mushrooms. The range of the potential hosts of helictines includes 53 species of fungus gnats from 26 genera. According to literature essentially added by the original data, the majority of the subfamily representatives is a group, where main or even the only known hosts are Diptera, and moreover, only the primitive represen- tatives of this order, such as fungus gnats (superfamily Sciaroidea, mainly Mycetophi- lidae). Most of them are mycetofagous. 194 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○The Finnish Environment 485 It should be noted, that orthocentrines are an essential component of entomofau- na in forest and especially in taiga ecosystems. In boreal forests, caracterized by pre- sence of rather cool, damp, shaded habitats, these ichneumon wasps could be extreme- ly numerous. According to my own experience, in a Malaise trap sample (Fig. 2), perma- nently operating whole season per different years in Karelia (Kivach Nature reserve) and in Finland (North Karelian Biosphere reserve), Orthocentrinae in various biotopes comprise from 11% (in herb-rich aspen forest) up to 23% (in Cladonia pine forest), 26% (Myrtillus pine forest) and even 34% (mixed forest) of all individuals ichneumonids, which, in turn, exceeded half of all hymenopterous insects. During a season this ratio strongly varied, reaching a maximum in September, up to 50-65%. 1 3 20 % 21 % 26 % 34 % 9 % 10 % 15 % 15 % 13 % 15 % 5 % 4 % 8 % 5 % 4 2 11 % 24 % 23 % 24 % 17 % 3 % 9 % 10 % 5 % 10 % 18 % 8 % 8 % 30 % Orthocentrinae Cryptinae Tryphoninae Ctenopelmatinae Campopleginae Ichneumoninae Other Fig. 2 Structure of the family Ichneumonidae in Malaise trap samples in different forest types: 1 - mixed forest (North Karelian Biosphere reserve, Finland); 2-4 Karelia, Kivach Nature reserve: 2 - Cladonia type pine forest, 3 - Myrtillus type pine forest, 4 - herb-rich aspen forest. Species composition and the population structure of Orthocentrinae in various forest types are similar: the representatives of genera Plectiscidea, Plectiscus and Orthocentrus dominate in all biotopes, making up to about 25% of all Orthocentrinae individuals. Other abundant genera in Eastern Fennoscandia, as well as in all taiga zone, are also Proclitus, Pantisarthrus, Helictes, Aperileptus and Stenomacrus. Speaking about the zonal and landscape distribution of Orthocentrinae it is pos- sible to assert that it is a group of ichneumon-flies with distinctly forest distribution. Within the Russian fauna the areas of the overwhelming majority of species (almost 90%) wholly or mostly are situated within the borders of a forest zone. In general, orthocentrine fauna of Eastern Fennoscandia is typical for taiga zone. The species with wide areas, mainly Holarctic and Trans-Palaearctic boreal areas prevail here. Outside the forest zone orthocentrines are not so abundant and occur mostly in mountain areas. For the present study based on materials from Eastern Fennoscandia new data adding faunistic lists of ichneumonids of Karelia and Finland were obtained. ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ The Finnish Environment 485 ○○○○○○○○○○○ 195 As a result of researches there are revealed, that 23 of these ichneumon-flies (Micro- leptes rectangulus, Cylloceria tenuicornis, Allomacrus subtilis, Aniseres caudatus, A. subarcti- cus, Hemiphanes performidatum, H. townesi, Gnathochorisis xanthocephala, Proeliator proprius, Eusterinx (Holomeristus) aquilonigena, E. (Holomeristus) minima, E. (Holomeristus) refracta- ria, E. (Trestis) trifasciata, E. (Divinatrix) inaequalis, Helictes carinatus, H. karelicus, Plectis- cidea fuscifemur, P. helleni, P. deviata, P. koponeni) have been found to occur in Finland and are recorded for the first time for the Finnish fauna. Within 9 species new for science, description of two has already been published and seven more will be published soon. Two species should be excluded from the Finnish list. Helictes