Ryan,
That's wax build up which excretes through the femoral pores.
It's perfectly normal and usually occurs around now (Spring) on
through the Summer or during breeding season. It occurs mainly
in males but also in some females.

Some believe the wax serves a purpose like marking/scenting
their territories during mating season. Others don't think it serves any purpose whatsoever.

If you clean/scrub his soiled ventral hind quarters, chances are
some or all the wax will simply fall off from the pores. If so, this will not bother him or affect his breeding season. Most keepers just ignore the waxy pores.

Good question btw,
John