The ootheca of Mastotermes darwiniensis Froggatt (Isoptera : Mastotermitidae): homology with cockroach oothecae

The basal termite Mastotermes darwiniensis produces an egg mass, the nature of which is controversial. The debate centres on whether it is homologous with the oothecae of mantids and cockroaches and, if so, whether its simple structure is plesiomorphic or apomorphic within the Dictyoptera. To help r esolve these issues we observed primary reproductives of M. darwiniensis du ring oviposition and examined the morphology of the reproductive product. O viposition is cockroach-like in that the egg mass is assembled within the v estibulum and the eggs are issued externally in pairs. The reproductive pro duct is an ootheca of the blattarian type. A distinct, tanned outer coverin g is stretched over the two parallel rows of eggs. No keel is present and n o calcium oxalate crystals were apparent in the outer covering. We cannot r ule out the possibility that the simple structure of the ootheca is plesiom orphic within Dictyoptera. However, based on (i) apomorphies shared by Mast otermes and Blattaria, and (ii) the life habits of Isoptera, a secondary re duction is the more plausible explanation.