Choice of character suite

Consequently, these subtle and gradual morphological differences lead to the questions of how many body characters should be measured and which ones should be chosen. Various body parts, falling into four main categories, have been used in morphometric analyses, starting with the first studies of Alpatov (1929): characters of body size, coloration patterns, wing venation characteristics, and characteristics of pilosity. Their descriptions are scattered over the literature, and the most commonly used characters are listed in Table 3. A core set of 36 characters selected for discriminative power is described in Ruttner (1988), containing the recognized measurements referred to as "classical morphometry".

Although most researchers utilize at least some characters from the above-mentioned set, the characters sets used in many studies vary considerably and deviate in the choice or number of these "standard" characters, and less than 10 are used in a number of studies. Occasionally, additional characters are introduced, but the selection of characters appears widely arbitrary. As comparisons between studies or to reference data rely on characters matching between data sets, these incongruities seriously compromise meaningful analysis. In consequence, to date it is difficult or impossible to piece together the patchwork of various comprehensive local studies that each must have involved significant amounts of labour, and much effort is wasted due to lack of consistency. As an orientation, in studies exploring unknown variation, we recommend to include the 25 characters proposed in Table 3, combined with wing shape analysis.