In anopheline larvae, the seta closely associated with and usually located posterior to the pecten below the posterolateral spiracular lobe; in other mosquito larvae, borne posterolaterally on the siphon; in species where more than one seta is borne in a similar position on the siphon, they are designated as seta 1a-S, seta 1b-S, etc. proceeding distad from the most proximal seta.
Larval chaetotaxy: seta 1-S