THE MICROHABITAT OF CULICOIDES-IMPUNCTATUS (DIPTERA, CERATOPOGONIDAE) LARVAE IN SCOTLAND

Soil samples were taken from two transects (total 63 sampling points; 25 cm quadrats) representing the Betula pubescens (Betulaceae) woodland, rush-pasture and peat-based mire vegetation of the west coast and Highlands of Scotland, in an attempt to relate soil and vegetation features to the occurrence of Culicoides impunctatus Goetghebuer larvae. The covers of vegetation groups were recorded at each sample site and soil wetness was assessed on an arbitrary scale. Culicoides spp. larvae were extracted from half of each sample and stored for subsequent identification of C. impunctatus larvae, while the remaining half was used for analysis of soil pH and organic content (loss on ignition, LOI). Correspondence analysis (using DECORANA) separated the sample sites and vegetation groups and the ordination axes were significantly correlated with the density of C. impunctatus larvae, soil organic content and soil wetness index. Simple regression analyses revealed that the density of Juncus acutiflorus/J. articulatus (Juncaceae) and soil wetness index were positively related to the overall variation in C. impunctatus larval density. The wetness index had the strongest relationship and this remained the case in step-wise multiple regression. There was no relationship between larval density and soil pH. This information on the specific microhabitat preferences of the larvae could aid colonization attempts of this dominantly important species of biting midge in the UK.