Argas (Microargas) transversus Banks (Ixodoidea: Argasidae): spiracular surface morphology and internal structure

The surface morphology and internal structure of the spiracle of Argas (Microargas) transversus were studied with the aid of light and scanning electron microscopes. The spiracle is described and compared with this organ in other ticks and in mites. Each spiracle, located lateral to coxa III, consists of an elongate, finely porous spiracular plate extending transversely laterad and onto the dorsal integument; basally a macula forms a lip that borders the ostium. Surface pores, arranged in a hexagonal pattern, lead into interpedicellar spaces bordered by pedicels in the spiracular plate cuticle. Internal to the ostium, a small subostial space leads into an obliquely directed atrial chamber from which tracheal trunks extend.