Previous observations have noted that in some species of higher termites the soldier caste lacks pigmented particles in its gut and, instead, is fed worker saliva that imparts a whitish coloration to the abdomen. In order to investigate the occurrence of this trait more thoroughly, we surveyed a broad diversity of termite specimens and taxonomic descriptions from the Old World subfamilies Apicotermitinae, Cubitermitinae, Foraminitermitinae, Macrotermitinae, and Termitinae. We identified 38 genera that have this "white-gutted" soldier (WGS) trait. No termite soldiers from the New World were found to possess a WGS caste. Externally, the WGS is characterized by a uniformly pale abdomen, hyaline gut, and proportionally smaller body-to-head volume ratio compared with their "dark-gutted" soldier (DGS) counterparts found in most termitid genera. The WGS is a fully formed soldier that, unlike soldiers in other higher termite taxa, has a small, narrow, and decompartmentalized digestive tube that lacks particulate food contents. The presumed saliva-nourished WGS have various forms of simplified gut morphologies that have evolved at least six times within the higher termites.

Department of Biosciences Centre for Ecological and Evolutionary Synthesis University of Oslo P O Box 1066 Blindern 0316 Oslo Norway

Department of Primatology Max Planck Institute for Evolutionary Anthropology Deutscher Platz 6 04103 Leipzig Germany

Faculty of Forestry and Wood Sciences Czech University of Life Sciences Prague Czech Republic

Fort Lauderdale Research and Education Center University of Florida 3205 College Avenue Davie FL 33314 USA

Leverhulme Trust Early Career Fellow School of Archaeology University of Oxford Oxford OX1 3QY UK

Okinawa Institute of Science and Technology Graduate University 1919 1 Tancha Onna son Okinawa 904 0495 Japan

UMR CNRS 5548 Communication Chimique Université de Bourgogne Développement 21000 Dijon France

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