Arachnon

From Tardis Wiki, the free Doctor Who reference

Arachnons were a spider-like sapient species with light blue shells. Their males were born in pairs of identical twins; they would seek out a mate together, and after fathering children with her, their wife would eat one of the two husbands, with the other one remaining to raise the children. The Arachnons themselves bemoaned this, but nothing could override this hormonal drive; male Arachnons consequently tended to seek out a life of excitement and adventure before they settled down to get married, knowing the risks. As a result, a lot of Arachnon art revolved around themes of love and death — though, as the Arachnons were quick to wittily point out, so was human art. (PROSE: Dreamstone Moon)