The distribution and dispersion of life stages of currant clearwing,Synanthedon tipuliformis(Lepidoptera: Sesiidae), in blackcurrant

Abstract

The distribution of life stages of currant clearwing, Synanthedon tipuliformis (Clerck), in blackcurrant bushes was investigated on two plots during 1971–75. Three ways of expressing the distribution are examined, none of which is totally acceptable. Generally less than 10% of eggs are found on the current season's growth, and since wood of this age group represents over 50% of the available universe, the proportion of eggs laid on it is relatively low. The proportion of the larval population in the younger wood increases until just before pupation, when over 80% of the population is in the most recent 2 years' growth. The 1-year-old wood harbours 50% of the early larval population, and a use for this information in assessments of the effectiveness of insecticide trials against adults is suggested. The dispersion of eggs and larvae of S. tipuliformis is shown by a number of indices to be aggregated. The frequency distribution is adequately described by the negative binomial. A common k, k _c, of 0.66 (95% confidence limits 0.57–0.80) for the egg stage was valid, but the k _c for the larval stage of 1.28 (1.09–1.56) was only marginally valid.