Impact of orphaning on field colonies of Southeast Asian Macrotermes gilvus (Hagen) and M. carbonarius (Hagen) (Termitidae, Macrotermitinae)

Field colonies of Macrotermes gilvus (Hagen) and M. carbonarius (Hagen) were experimentally orphaned to examine their potential for producing replacement reproductives. Orphaned colonies were investigated only once for caste composition at selected time intervals at 3, 6, 9 or 12 months after orphaning. Of the 38 orphaned colonies of M. gilvus, 15 colonies (39.5%) re-established. In M. carbonarius, three colonies out of 20 (15%) re-established. Re-established colonies were headed by adultoids which were morphologically indistinguishable from primary reproductives. In naturally orphaned colonies of M. gilvus, we often found multiple adultoids with normal pigmentation but torn wings, i.e. the colonies retained alates as replacement reproductives. The number of reproductives probably declines over time. It may take alates of M. gilvus 6 months to develop into functional adultoids, and up to 12 months for alates of M. carbonarius. Our results also demonstrate that the presence of sexual castes (nymphs or alates) at the time of orphaning does not necessarily guarantee the success of colonies in re-establishing themselves as breeding colonies. We also found a high prevalence of occupation of the mounds by other termite species, after the death of M. gilvus (18.4%) or M. carbonarius (30.0%) colonies, probably using them as foraging sites.