Microclimatic conditions influence on fungus gnats (Diptera, Sciaroidea, excl. Sciaridae) territorial distribution

The fungus gnats (Sciaroidea, excl. Sciaridae) are a large group of Diptera, which have more than three thousand species. Representatives of this superfamily prevail in mushrooms of the wet shadowy forests of Siberia. It is typical for them to form multispecies aggregations in appropriate shelters like wet pits, tree hollows, etc. The fungus gnats fly intensively outside these shelters in cool dull weather conditions. We investigated the influence of the microclimatic conditions on the characteristics of the distribution of the fungus gnats. From July 20 till August 7, 2009 the measurements of temperature and humidity had been taken, catching and quantitative registration of gnats had been carried out. The observations registered that microclimatic conditions in the fungus gnats shelter (a wet pit with a grotto formed by the roots of an old birch) are more constant than in the biotope. In the pit the humidity is 65-100% and the range of the temperature fluctuations is smaller. The analysis of the study showed that the change of humidity influenced the degree of aggregation of the midges significantly. After relative humidity dropped below 65% the midges attempted to find a shelter where the microclimatic conditions were favourable. The quantity of the midges in shelters was many times larger than at the points of biotope outside this shelter. The average quantity of the midges collected in the pit was 19.4 specimens over one registration; in the points of reference this value was 2.5 exempl. per excerpt. The cool and wet period conditions contributed to intensive mobility of the fungus gnats and their distribution over the forest became more incidental. The average quantity of midges collected in the pit and at the points of reference was almost equal: 4.7-6.2 specimens in the morning hours and 9-11.3 specimens in the evening ones. Thus, the distribution of the midges can be aggregated or incidental depending on humidity and temperature conditions. Such features of the fungus gnats behaviour must be taking in account in the process of selection of the methods for imagoes catching in natural conditions. In the afternoon, especially during the period of hot, dry and sunny weather, catching of midges in the places of their aggregation is most effective. Using different types of traps or scything grass with an entomological net are more effective any other time

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