This family of proteins represents the complementary sex determiner in the honeybee. In the honeybee, the mechanism of sex determination depends on the csd gene which produces an SR-type protein. Males are homozygous while females are homozygous for the csd gene. Heterozygosity generates an active protein which initiates female development [2].

1: The gene csd is the primary signal for sexual development in the honeybee and encodes an SR-type protein. Beye M, Hasselmann M, Fondrk MK, Page RE, Omholt SW; Cell. 2003;114:419-429. PMID:12941271

2: The dice of fate: the csd gene and how its allelic composition regulates sexual development in the honey bee, Apis mellifera. Beye M; Bioessays. 2004;26:1131-1139. PMID:15382141