The vertical distribution of Culicoides impunctatus larvae

Soil cores were taken from three transects, representing the vegetation typical of much of the west coast and Highlands of Scotland, in an attempt to investigate the distribution of Culicoides impunctatus larvae. Sampling of soil cores was carried out at four periods throughout the day (00.00, 05.00, 12.00 and 17.00 hours). Each core sample was sliced into sections, 1 cm deep and Culicoides impunctatus larval numbers in the first 8 cm of the soil core were investigated, using a sugar-flotation technique. At all sampling times, approximately 50% of the total numbers of larvae recovered were from the first 2 cm of the soil. During the daylight sampling periods (05.00, 12.00 and 17.00 hours), there was a small but significant migration of larvae into the deeper layers (2-5 cm). The results are discussed in relation to those for other species from previous studies, and also to their application in larval collection for colonization techniques and in localized Culicoides control.