part of adult mesopostnotum antecostal suture Fig 12,19 Abbr: AtS in ISBN:0-937548-00-6. TGMA:0000399 TGMA:0000399 The external groove of the antecosta. That of the antecosta bearing the first phragma is not readily visible in mosquitoes. Antecostal sutures have not been studied or recognized in the abdominal segments of most mosquitoes but are known to occur on the terga and sterna of abdominal segments II and III in Culiseta inormata. default_namespace