On the use of instar information in the analysis of subfossil chironomid data

Abstract

Head capsules of chironomids of the genera Chironomus, Glyptotendipes and Microtendipes in two cores from Lough Neagh, Northern Ireland, were identified to instar. The proportions of 3rd and 4th instars did not stay constant throughout the lengths of the cores and it is possible there was differential preservation of the instars. Plotting diagrams using only one instar could give misleading information about the occurrence of a genus, while plotting total number of head capsules may result in individuals being counted twice. Counting the most numerous taxon at each level in the sediment avoids the latter problem while retaining maximum information about the fauna. Non-metric Multi-Dimensional Scaling ordination diagrams calculated using the different methods illustrate the similarity of plot obtained.