Effects of light-trap design and illumination of samples of moths in the Kenya highlands

The effect on the size of sample of 32 taxa of Macrolepidoptera, and on the index of diversity α, of various modifications of the light in Rothamsted and Muguga light-traps was investigated in experiments at Muguga, Kenya, in 1968. The sample of moths from the standard Muguga mercury-vapour trap was fifty times as big as that from the standard Rothamsted Tungsten trap. Using a mixed mercury-vapour and tungsten lamp in a Muguga trap halved the sample, as also would obscuring 60% of the light from a standard mercury-vapour lamp. Overall size of sample, direction of illumination and source of illumination all affected the proportion of different taxa in the sample, but the diversity index differed little in any of the combinations of traps, lamps and sites. Analysis of the pattern of sample distribution over the site showed that moths of all sizes were migrating downwind and height of flight was found to be positively correlated with size. Interaction between traps and sites, combined with the differing heights of flight of the different taxa, complicated the definition of specific sample size; a three-dimensional representational model attempts to define the spatial population parameters required to define the specific sample. RESP-660