thanks for the link for the mexican red rumpThere are numerous "red rump" tarantulas that look very similar. Many of them are from genus Brachpelma. Vagans, sabulosum, and angustum are some of the more common brachypelma species. Less common is Sericopelma rubronitens. Fortunately, the care instructions for these are similar.
http://www.eightlegs.org/redrump/vagans.html