Schadinia okana Lipina, 1939 – synonym of Demicryptochironomus vulneratus
Sergentia profundorum Kieffer, 1922 – synonym of Sergentia coracina
Smittia giordanisoikai Marcuzzi, 1949 – synonym of Thalassosmittia thalassophila
Smittia orientalis Konstantinov, 1952 – synonym of Georthocladius luteicornis
Spaniotoma (Trichocladius) foveata Edwards, 1929 – synonym of Rheocricotopus atripes
Spaniotoma cheethami Edwards, 1929 – synonym of Parakiefferiella bathophila
Spaniotoma hospita Edwards, 1929 – synonym of Eukiefferiella claripennis
Spaniotoma tripilata Edwards, 1929 – synonym of Synorthocladius semivirens
Stempelina septentrionalis Chernovskij, 1949 – synonym of Constempellina brevicosta
Stempellina montivaga Goetghebuer, 1934 – synonym of Stempellina bausei
Stictochironomus rezvoji Chernovskij, 1937 – synonym of Omisus caledonicus
Stylotanytarsus luteola Goetghebuer, 1950 in Thienemann, 1950a – synonym of Paratanytarsus grimmi
Syncricotopus fontinalis Saether, 1969 – synonym of Paratrichocladius rufiventris
Syndiamesa pilosa Kieffer, 1924 – synonym of Pseudodiamesa branickii
Syntanytarsus (Eutanytarsus) trivialis var. frontinalis Kieffer, 1915 in Thienemann, 1915 – synonym of Micropsectra apposita
Syntanytarsus (Eutanytarsus) trivialis var. salita Kieffer, 1915 in Thienemann, 1915 – synonym of Micropsectra apposita