External morphology of the quiescent instars of trombiculid mites (Acariformes: Trombiculidae) with notes on their moulting processes

The morphology and cuticular ultrastructure of the quiescent instars prelarva, proto-and tritonymph of the trombiculid mites, Hirsutiella zachvatkini, Leptotrombidium orientale and Leptotrombidium schlugerae (Trombiculidae) were investigated with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Their post-embryonic life cycle is considered in terms of their moulting processes. The existence of the quiescent instars in mite ontogenesis is determined by the presence of the cuticle being closely appressed to the hypodermis irrespective of whether the old cuticle occurs or not, and is limited to a relatively short time, approximately at the middle of the entire inactive period. The quiescent instars possess non-articulated reduced legs and mouth parts as well as slightly tuberculate and folded cuticle without setae.