Distribution of leg sensilla chaetica in male Chironomidae (Diptera) and its phylogenetic significance

Abstract

AbstractThe hair-like sense organs found on the tarsomeres in Chironomidae can be classified as sensilla chaetica (SCh). They are of three different types and there are indications on the presence of a fourth type. SCh are present in many groups of insects but the particular shape of their tips in one of the types developed within the Chironomidae seems to be unique. They are present in males of all subfamilies except Aphroteniinae and Telmatogetoninae. Within the different evolutionary lines two trends are found in the distribution of the studied type of SCh: (1) In the plesiomorph taxa SCh are found on P2 while in the more apomorphic ones they are found on P2 and P3 or only on P3. (2) The position of the SCh tends to move from a basal position in the plesiomorphic taxa towards a more apical position in the more apomorphic taxa. These two trends are found in several evolutionary lines. This tendency for a parallel development restricts the phylogenetic use of these trends to taxa already delimited by synapomorphies.