The female has a rust haze on her back while the male is solid, slick black. Pairs usually feed close together after pair bonds have been established. Right now there quite a few match making fights still going on at the "PITS".
The female initiates breeding when she assumes this head down tail up position. I've never been able to determine exactly any particular action that imediately preceeds this stance but usually I can tell something is about to happen and watch for the show to begain.