The following is a selection of Archytas sp. from both French Guiana and Brazil showing some of the immense diversity of this genus. Despite their huge variability Archytas spp. usually have a characteristic change in colouration between tergites 1-4 and tergite 5 – the whole abdomen is shiny but tergites 1-4 have a faint, pale bloom (not dusting) while tergite 5 is just shiny and a bit darker.
EDIT (6/8/2011): After a visit to the BMNH last week I am quite sure that the first specimen (from Brazil) is probably Archytas aurifrons. My specimen matches the specimens in the museum but of course there could be other species that are not in their collections.
Determinations by Monty Wood.