Distant (1899a) synonymized Coptosoma bellulum Walker, 1867, C. concinnulum Walker, 1867, C. inclusum Walker, 1867, C. pygmaeum Montandon, 1896, C. saundersi Lethierry & Severin, 1893, and C. siamicum Walker, 1867 with C. sphaerula. Later, Distant (1901h) concluded that all the names are synonyms, with the oldest one, Coptosoma siamicum, valid. The latter, however, is not identical with C. sphaerula. Yang (1934a) synonymized C. siamicum with C. variegatum Herrich-Schaeffer, 1838. Coptosoma microstigma was synonymized with C. sphaerula by Distant (1899a), but later not cited by him (Distant, 1901h, 1902a) in synonymy of neither C. sphaerula nor C. siamicum.