Down here in Melbourne it is very unlikely to find a didj with a "sugarbag" beeswax mouthpiece than further north like Cairns as the sugarbag bee is native more to warmer Australia. So the local didj makers here use an alternative to the native beeswax. They mix charcoal with commercial beeswax which forms a black and slightly more rigid mouthpiece than normal beeswax or sugarbag and thus it keeps the desired shape longer. The major drawback is that it heats up and softens if left in the sun because of its darkness
I find the black wax gives a more "earthier" look on didjes and seems to work with both plain and painted didjs (obviously depending on the artwork and you personal preference). The dark wax also doesn't show all the dirt, dust and hairs that make plain wax go so murky and thus seems to give a more hygienic impression. The wax mouthpiece still suffers from modification problems when your friends play it but less severe than plain wax.
Scott Endersby writes:
The bee that we are speaking about is named
Trigona carbonaria (Australian Native Stingless Bee)
I believe this bee is the most common producer of a Sugar bag nest. The name "Sugar bag" I think is a translation of the Aboriginal name for the nest. Although there are many bees in Australia I believe this would be the most common one. But now that you have put me to my word I shall keep studying this subject and will keep you up to date with what I find out..