. Bonner zoologische Monographien. Zoology. FIG. 7. Typical acarine body plan, with gnathosoma and idiosoma. Letters from "C" to "PE" are names for segments [modified from Moritz et al. (1994)]. Tapping contacts, as they have been reported, , for Limnesia maculata, could serve as a preadaption to semi-direct and direct sperm transfer as well as to copulation — a behavior developed convergently se- veral times in the more recently derived Hygrobatoi- dea (). In many Hygrobatoidea (), the body form, or the form of a leg or leg segments, is altered in order to allow
. Bonner zoologische Monographien. Zoology. FIG. 7. Typical acarine body plan, with gnathosoma and idiosoma. Letters from "C" to "PE" are names for segments [modified from Moritz et al. (1994)]. Tapping contacts, as they have been reported, , for Limnesia maculata, could serve as a preadaption to semi-direct and direct sperm transfer as well as to copulation — a behavior developed convergently se- veral times in the more recently derived Hygrobatoi- dea (). In many Hygrobatoidea (), the body form, or the form of a leg or leg segments, is altered in order to allow the sexual partner to attach, transport or store the spermatophores produced by the males. The sexual dimorphisms in these characters or in the structures of the genital region (valves, acetabula) are common not only among Hygrobatoidea {sensu Tuzovski 1987) but also in most other superfamilies. Harveys (1998) comment on earlier clado- gramms published by Witte (1984, 1991) is valid as well for the one of 1999 presented below (Fig. 6). Harvey points out that the cladograms published by Witte (1984, 1991) are not accompanied by a char- acter matrix and are therefore difficult to assess. Analysis of this phylogeny is further hampered by the limited number of terminal clades (about 40 species out of 20 genera are included, presumably as exem- plars of higher taxa). However the large number of characters utilised, particularly of spermatophore mor- phology and mating behaviour, shed considerable light on the evolution of these character systems with- in the context of the Parasitengona. General morphology Hydrachnellae exhibit the characteristic acarine body plan (Fig. 7) with a body divided into gnathosoma and idiosoma. The anterior region or gnathosoma bears the chelicerae and the palpus. The posterior region or idiosoma (body proper) externally bears the legs, reproductive structures and the anus. The podosomal and opisthosoma! separation, typi- cally for ancestors of the Acar
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