Have you browsed our sexing forum, where you posted this thread? There's a thread near the top saying "Pandinus spp. and Heterometrus spp." and it tells you how. There's also a bunch of emp threads where people have asked about their scorpion and been given an answer, and since they're sexed the same way, these threads are a good reference.
The only thing that sets H. longimanus apart from the others is that adult males have very long chela, but that's only useful if you're distinguishing between a few adult specimens.
