Scanning electron microscopic observations on the mouthparts of Panonychus citri (McGregor) (Acari: Tetranychidae) and Agistemus terminalis (Quayle) (Acari: stigmaeidae) on satsuma mandarin

A comparative study of the mouthparts of Panonychus citri (McGregor) and Agistemus terminalis (Quayle) were conducted under scanning electron microscope. In P. citri, the palpus is five segmented and irregularly striated. The palpotarsus has three setae, three sensory organs and one smooth surfaced palpotarsal eupathidial spinneret. The palpotibia has comparatively small claws. The stylophore is comprised of irregularly striated basal and horizontally striated distal segments. The stylets are smoothly surfaced and originate from the ventral portion of fixed digits. The rostrum has an elevated lip of rostral gutter on its dorsal surface and a membranous flap on the ventral and lateral sides. The cheliceral stylets are cylindrically concave and reveal a rod-shaped food channel in the mesal region. While in A. terminalis, the palpus is also five segmented, a portion of the second segment is striated and the others are smoothly surfaced. The palpotarsus has a cylindrical and roughly surfaced sensory organ which exhibits a branched slender trifid sensillum at the apex. The palpotibia has bigger sharp claws, thicker at the base and roughly surfaced. The stylophore consists of a membranous basal and smoothly surfaced distal segments. The rostrum has a membranous overlap on the dorsal surface extending up to the rostral cavity.