This is an extremely interesting phenomenon, rarely reported for temperate bees (Janscha 1771; Knight 1807). but commonplace in Africa (Hepburn 1993). It is well documented for some, but not all African honeybee races (adansonii, capensis, scutellata, intermissa). 

Observations on amalgamations range from the merger of two queenright dwarf swarms in capensis (Hepburn & Whiffler 1988) to the extraordinary photograph of an adansonii mega-swarm in Zambia (Silberrad 1976). For the latter a rough calculation shows that the volume of bees entirely enswathing a large tree is of the order [0.85 cubic meter]  or about [12,000,000] bees, the equivalent of 300 or so very strong colonies. This must be seen as an extreme case and has not been reported from Zambia by apiculturalists since then (B. Clauss, pers. comm.; T. Chupa, pers. comm.). 

More usually one encounters a few to several dozen queens in a conglomerate swarm. Our most detailed observations for Africa come from Donaldson (1982) who described the movements, mergers and separations of eleven small scutellata swarms over six days. Local conditions around the apiary in the northern Transvaal, South Africa were midwinter (July dry season), and conspicuous flowering plants included Aloe and Rhus thinly scattered in the veld. Donaldson (1982) observed the movements of the eleven small queenright swarms between two trees. With limited fighting the swarms coalesced, separated and then coalesced again. The final result was the formation of three substantially larger colonies that moved into empty hives followed by the shedding or elimination of eight supernumerary queens. 

Amalgamation varies in that there is sometimes fighting and sometimes not. In any event an almost universal feature is that when such polygynous swarms eventually settle in a cavity, or are hived, the supernumerary queens are almost always killed, thus restoring monogyny. For capensis it was shown that for conglomerates of migratory swarms there was a positive correlation between colony size and the number of queens (all mated) in a conglomerate (Hepburn & Whiffler 1988). The same authors analysed the mandibular gland constituents of the queens from these polygynous swarms and found no significant differences in paired comparisons with queens from settled monogynous colonies. The possible interplay of pheromones under conditions of amalgamation remain totally enigmatic. 

Honeybees Of Africa
by H. R. Hepburn, Howard R. Hepburn, Sarah E. Radloff

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