When I've compared these in the past, I've concluded that mesomelas/sp always have a black head/thorax and in sparshalli it can be either black or white; and that some sparshalli are yellowish.
The head appears to be obscured, but like this sighting : there are male T. mesomela with brownish hairs around the thorax at eg (IM08-2542) CC BY-NC-SA (2011) on the BOLD page http://www.boldsystems.org/index.php/Taxbrowser_Taxonpage?taxid=328300