Melissotarsus species: Bee-legged ants

MYRMICINAE

Melissotarsus emeryi (Forel, 1907):
Bee-legged boring ant

Size: 2.75 to 3.5 mm; overall yellowish brown. The flattened antennae have only six segments [scape + five]; the two apical segments form a strong club. Mandibles darker brown with a strong apical tooth that appears worn away in older individuals. Small oblong eyes in front of the midline of the head. The alitrunk or thorax is box-like, the segments fused, and without any spines, but strongly grooved. The legs are extraordinary: the coxae of the middle and hind legs are enormously enlarged, as is the femur of the hind pair of legs. What’s more, the upper tarsus of each leg is greatly swollen, especially the middle and hind legs, and terminates in a ring of teeth or scales that resemble nothing so much as finger nails!
These thickened upper tarsi give the legs a bee-like appearance, hence the name, from the Greek melissa = honey bee, and tarsus = leg. Bizarrely, the ants walk with the fore- and hindlegs on the floor in the normal fashion, but with the central pair of legs walking on the ‘ceilings’ of their tunnels.
The ants are fairly hairy, with shorter and longer fine, long, pale yellow hairs.

These extraordinarily bizarre little ants live under the bark and in the heartwood of living trees and shrubs, never emerging except perhaps to see off alate reproductives – males and females – on their way to mate and establish new nests. Consequently the ants are very seldom seen and are only likely to be found in branches freshly broken by the wind – or by wilful destruction of protected flora! Coccids or mealy bugs are always present in the nests and it appears that the ants rely solely upon these for food. How the coccids get into the nests is unknown, but it seems possible that, just as in the case of the Yellow Forest Sugar ant [Acropyga arnoldi], a few coccids fly away attached to the hairs of the alate reproductives and so are present when the new colony starts.
These ants are true wood-borers [unlike the so-called ‘carpenter’ ants, the favoured common name for Camponotus in America] and it seems likely that the teeth on the legs as well as the strong apical teeth on the mandibles are used in tunnel construction.

In the Western Cape the ants have so far only been found living in Leucospermum praemorsum shrubs (Nardouw fountain pincushion), a handsome protea that occurs in quite large numbers but spread over a few very localised areas. There is no information to hand over which plants they inhabit in KZN, Mpumalanga or Zimbabwe, but it would be interesting to know whether in these areas they also inhabit Leucospermum. If so these would most probably be L. innovans and L. saxosum – or they could be inhabiting various Faurea or even Protea species. It seems perfectly possible that even the Western Cape they may be yet be found in a wider range of plant species.

There are only four recognized species in the genus, one in Madagascar [where it is rare] and three in Africa, where they are uncommon but widespread. There is some doubt about the separation of the African species. Based on characteristics of the very few reproductives that have ever been found, the differences between species may turn out to be superficial and they’ll all end up as one species after all. Melissotarsus emeryi in our region occurs in the Western and Northern Cape as well as Zimbabwe, while the absolutely similar M. beccarii is from KwaZulu-Natal and Mpumalanga.