part of spinning field of anterior lateral spinneret major ampullate field spider_anatomy A partly sclerotized sector on the spinning field of the anterior lateral spinneret, bearing the major ampullate gland spigots and associated sensilla. Some of the relatively basal Araneomorphae (filistatids, eresids) have, in addition to a mesal marginal cluster, one or more major ampullate spigots mixed among the piriforms. SPD:0000255