Abstract
SUMMARY: The tegumental surface of Schistosoma margrebowiei as viewed by scanning electron microscopy is described. Both spined and unspined tubercles were found on the dorsal and dorso-lateral surfaces of sexually mature (in copula) male worms. Unpaired males lacked spined tubercles and the development of the spines is considered to occur only when worms are in copula. The females lack tubercles. The importance of tubercle structure in the identification of schistosome species and the effect of sexual maturity on their development is discussed.