The subgenus Persicargas (Ixodoidea: Argasidae: Argas). 34. Larval respiratory system structure and spiracle formation in pharate nymphal Argas (P.) arboreus

Structure of the larval respiratory system and spiracle formation in pharate nymphal (N sub(1)) Argas (Persicargas) arboreus) are described as seen by light and scanning electron microscopy (SEM). Paired ostial apertures in folded integument between coxae I and II, observed by SEM in unfed larva, are replaced by coxal pores in the pharate nymph. A perforated spiracular plate, enclosing a wide ostium and lacking macula, forms the N sub(1) spiracle situated dorsad to each coxa III. Air passage in the larval respiratory system is probably controlled through interlocking of spiny projections in the vestibule wall and/or luminal collapse of the vestibule by muscle contraction. Air passage is controlled in the N sub(1) by a valve between the subostial space and atrial cavity.