Differentiation of external morphology of Oribatulidae (Acari: Oribatida) in light of the ontogeny of three species

In this paper the differentiation of external morphology and ontogeny of Oribatulidae were investigated, on the basis of Phauloppia lucorum (C. L. Koch, 1841), Lucoppia burrowsi (Michael, 1890), and Oribatula tibialis (Nicolet, 1855), which ontogeny is described and illustrated here for the first time. The juveniles of these species have smooth cuticle, a clavate sensillus with barbed head, and similar formulae of coxisternal, genital and aggenital setae, but differ mainly in body size, formulae of gastronotal setae, number of setal excentrosclerites on the gastronotum, and shape of some setae. The number of setal excentrosclerites and presence of seta h(3) in larva differ the juveniles of Ph. lucorum and L. burrowsi from those of O. tibialis, and seem to have generic value, and are also associated with the number of notogastral setae in adults (14 pairs in two former species, 13 pairs in latter species). The juveniles of O. tibialis lack excentrosclerite at seta lm, comparing to those of Ph. lucorum and L. burrowsi, and this morphological character is shared with Scheloribates Berlese, 1908 and Liebstadia Oudemans, 1906 from the family Scheloribatidae. The larva of O. tibialis lacks seta h 3, similarly as that of Scheloribates, while the larvae of Ph. lucorum, L. burrowsi, and Liebstadia have this seta. Presence of setal pair c 3 in adult of Zygoribatula cf. frisiae (Oudemans, 1900) is recorded here for the first time, which indicates the order of loss of setae of c-series in Oribatulidae according to Grandjean (1951, 1958, 1968).