Xiphomyrmex costatus subsp. willowsi Wheeler, 1934a: 177 (w.) SOLOMON IS (Malaita I., San Cristoval I.). Australasia.

Primary type information: Primary type material: 2 syntype workers. Primary type localities: 1 syntype Solomon Is: Malaita I., Uras Cove, 28.v.1933 (M. Willows), and 1 syntype San Cristoval I., Star Harbour, 1.vii.1933 (M. Willows). Primary type depositories: CASC, MCZC.