Phylogenetic significance of antennal growth patterns at two levels of dragonfly taxonomy: the example of Cordulegaster (Anisoptera: Cordulegastridae)

In the course of postembryonic development of an odonate larva, the number of antennal segments increases from 3 in newly hatched larvae to 7 in most full-grown larvae. New segments are formed through division of existing segments with the construction of new joints. 2 growth or division centers in the odon. antenna are responsible for this joint formation. A third growth center does not form new joints, but stimulates extension of existing segments. — Ontogenetic studies on 2 spp. of Cordulegaster demonstrate the phylogenetic significance of antennal growth pattern at 2 levels of dragonfly taxonomy. At the family level, differences in the operating sequence of the 2 division centers determine a variety of basic antennal growth patterns. The sequence of divisions observed in C. insignis and C. pictus is in agreement with the position of the Cordulegastridae in the currently accepted genealogy of the order. — Minor but significant interspecific differences in antennal development among W. Palaearctic Cordulegaster constitute a key character to differentiate between taxa belonging to the C. boltonii and C. bidentatus species groups. Biometric analysis of immature larvae of C. ins ignis (C. bidentatus group) and C. pictus (C. boltonii group) explain these differences as being due to a subtle difference in the original position of the division centers, rather than to allemetric growth of antennal segments during larval development.