The subgenus Persicargas (Ixodoidea: Argasidae: Argas). 38. Haller's organ roof and anterior pit setae in Persicargas and Microargas.

Adults of 13 of the 17 species constituting the subgenus Persicargas (parasitizing birds nesting in trees) and the single species of the subgenus Microargas (parasitizing the Galapagos giant tortoise) were studied by scanning electron microscopy. The setae of the anterior pit of tarsus I number nine(1 serrate, 1 setiform, 1 conical, 2 fine, 2 porose, 2 grooved) in Persicargas. The single, serrate seta arises from an anterior section of the pit, the other eight setae arise from a posterior section. Abnormally, fewer or more setae occur on one or both tarsi of a single specimen. The setal arrangement is similar in Microargas, but the total number is eight (setiform seta absent). The capsule roof of Haller's organ in Persicargas is typically flat and platelike with a circular central aperture and few to moderately numerous small perforations. Thus, this roof is more solid than in other subgenera of Argas, except in Microargas and subgenera associated with cave-dwelling bats (Carios and Chiropterargas). The roof structure is quite variable in samples of A. (P). radiatus. The roofs of two Persicargas species differ from the typical pattern, the A. (P.) minatus roof is more extensively perforated and in some specimens of A. (P.) streptopedia the roof is netlike. The Microargas roof, on a sloping surface bounded by a transverse anterior groove, is more solid than those of Argas and has a circular aperture surrounded by small perforations. The biological implications of these structural properties should be investigated.