Observations on the ontogeny of halarachnid mites (Acarina: Halarachnidae).

Descriptions are given of protonymphal and deutonymphal instars of Orthohalarachne diminuata (Doetschmann 1944) and O. attenuata (Banks 1910), together with comparative data for larvae and adults. Some phylogenetic implications of comparative ontogeny in halarachnids are considered. Leg and palpal chaetotaxy of all instars of Pneumonyssus simicola, Banks 1901 is compared with that of the two Orthohalarachne species and with that characteristic of free-living dermanyssids. A neotenic pattern is indicated for the three species of halarachnids. Differences of probable generic significance in leg and palpal chaetotaxy are described for the three species mentioned and for Halarachne Allman 1847.