Bothriomyrmex ants

Bothriomyrmex ants are social parasites whose queens take over another ant species’ nest by removing its queen and relying on the surviving workers to rear parasite offspring. The account presents this takeover as an example of the extended phenotype: a parasite’s effects can reach beyond its own body and alter the behavior of a host in ways that benefit the parasite’s genes.

Parasitic queens and host nests

The book identifies Bothriomyrmex regicidus and Bothriomyrmex decapitans as parasites of other ant species. Because ant young are normally fed by workers rather than by their parents, a parasitic queen must gain the cooperation of the host workers. Removing their mother, whose continuing reproduction would produce competing brood, is the first step in this change of control.

A queen enters the host nest alone, finds the host queen, and kills her. The host workers then adopt the parasite queen and tend her eggs and larvae, initially without recognizing the change in whose offspring they are raising. The takeover thus converts the existing colony’s workforce into care for a new reproductive line.

Replacing the colony

Some of the parasite’s offspring mature into workers and gradually replace the original species in the nest. Others become queens, leave to establish themselves elsewhere, and continue the cycle. The outcome is not merely the survival of one invading queen: over time, the parasite’s offspring can displace the host species from its own colony.

The account emphasizes the contrast between the queen’s solitary entry and the colony-wide consequences that follow. Once the host queen is gone, the workers’ ongoing care supplies the labor that the parasite queen would otherwise lack. The workers’ service sustains the parasite’s brood and helps produce the next generation of queens.

Significance in the extended phenotype

The example belongs to a broader argument about parasites that change their hosts. A parasite can benefit when a host survives, but the interests of host and parasite diverge when their genes leave the host by different routes. The book proposes that when parasite genes are not transmitted through the same vehicles as host genes, the parasite may be expected to damage or exploit its host rather than promote the host’s reproduction.

Bothriomyrmex ants make that argument behavioral: the host workers’ actions become part of the parasite’s reproductive success. The example sits beside other cases in which parasites influence host development or reproduction, and it sharpens the question the book proposes asking of any apparent behavior: whose genes benefit from it? Here, the workers’ care keeps the colony functioning, but the reproductive beneficiaries are the invading ants.