91. Halobates mariannarum Esaki, Tenthredo 1: 357, 1937.

Thirteen specimens, Piti, May 12, Usinger; 50 specimens, Piti, May 22, Usinger; four specimens, Tumon Beach, May 30, Usinger; one specimen, Tumon, April 22, Bryan .

Described from the nearby island of Rota.