What is the learned behavior of a Black Widow Spider?

It eats the male spider while matting.

During matting, the male have it's abdomen against the female fangs.While the male get it's palp to the female epygine the female can eat the male's abdomen. Some member of the Black widow's genus ( family:Theridiidae; Latrodectus hasselti & Latrodectus geometricus ) have a constriction in their abdomen which allow them to get the first half eatten and then come back to matte once more. It's usefull since each male have 2 palp to empty of sperm and they can only do once per matting.

Herberstein, M. E. (Ed.). (2011). Spider behaviour: flexibility and versatility. Cambridge University Press.