The microhabitat ofCulicoides impunctatus(Diptera: Ceratopogonidae) larvae in Scotland

Abstract

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.

Selection of resting areas by emergingCulicoides impunctatus(Diptera: Ceratopogonidae) on downy birch (Betula pubescens)

“…The study was carried out on the Ormsary Estate, Argyllshire (NR 743 724), 'Clachbreck', which has been previously described with regard to C. impunctatus microhabitat preference (see Blackwell et al 1994 for detailed description). This was a southnorth valley, conforming to type W4 of the National Vegetation Classification: Betula pubescens -Molinia caerulea community (Rodwell 1991) and possessing an open canopy.…”

“…Following these initial studies, sticky trap inserts (Oecos Ltd, Kimpton, UK) of 10610 cm area and coated in adhesive on the outer facing side, were fixed to 10 randomly selected downy birch trees (Betula pubescens), in an area of known C. impunctatus breeding habitat (as defined by Blackwell et al 1994). Traps were placed at four heights (1, 2, 3 and 4 m from ground level) and on four faces at each height (north, south, east and west, as defined from compass readings).…”

Collection ofCulicoides(Diptera: Ceratopogonidae) Using CO2and Enantiomers of 1-Octen-3-ol in the United Kingdom

“…Experiments were conducted in Ormsary, Argyll, Scotland (55Њ 55Ј 27.73 N; Ϫ5Њ 34Ј 15.80 W), an area with a well studied population of C. impunctatus [for further details of area see Blackwell et al (1994bBlackwell et al ( , 1999], using a series of Þve Mosquito Magnet Pro traps (American Biophysics Corporation, North Kingston, RI). The machines were placed 50 m apart in an area of birch (Betula pendula/B.…”

Repellent efficiency of BayRepel against Culicoides impunctatus (Diptera: Ceratopogonidae)

“…The area used was contiguous with habitat that is known to support larval populations of C. impunctatus (Blackwell et al 1994). During trials, both treatment and control forearms of the subject were exposed to midges following an initial period of 3 min to allow densities of host-seeking insects to stabilise.…”