This species appears to be a specialized associate of small Attini (Wheeler 1925, Brandao 1990, Adams et al. 2000), a habit possibly shared with other species of Megalomyrmex such as wettereri, mondabora, and silvestrii. Wheeler (1925) found numerous colonies nesting with Sericomyrmex amabilis on Barro Colorado Island, Panama. He observed a number of colonies in the lab, and made the following observations:The colonies of the Cepobroticus [Megalomyrmex symmetochus] so frequently found living with Sericomyrmex amabilis were decidedly less populous than those of their host. The largest comprised less than 75 individuals, and often the number did not exceed 40 or 50. In every nest a dealated mother queen was present. She usually took up her station, surrounded by a group of her workers, in one of the crypts of the fungus garden a short distance - half to three quarters of an inch - from the Sericomyrmex queen. The guest ants kept their brood in small clusters scattered through the garden and each cluster was cared for by a few workers. Although the ants and their brood were thus intermingled, the workers of each species lavished their attention exclusively on their own eggs, larvae and pupae and were never seen even to transport the progeny of the other species from one part of the garden to another.The workers and queens of Cepobroticus are rather alert and move about more rapidly than their hosts. They devote so much time to licking and fondling one another that the observer is somewhat astonished to find them paying little or no attention to the fungus-growers. As a rule the two species are indifferent to one another. One may watch them for hours without observing anything more than rather distant, mutual antennal salutations. On rare occasions a worker Cepobroticus may be seen licking the gaster of a Sericomyrmex worker or of the sluggish queen. More frequently one of the host workers may be observed in the act of lavishing similar but more elaborate attentions on a Cepobroticus worker. The fungus-grower begins by licking the feet or tarsi, the tibiae and femora, then the thorax or abdomen and finally the head and even the mandibles of the guest. During this operation the latter remains motionless and inclines its body somewhat to one side.The Sericomyrmex never feed their guests by regurgitation. This is not surprising because they never feed one another thus, but resort individually to the growing fungus bromatia. When hungry the Cepobroticus workers and queen also crop the fungus mycelium, but they do this rather roughly, using their mandibles and even shaking or disturbing the substratum. The guests very rarely transport or rearrange the particles of the substratum or take the slightest interest in the garden, except as a source of nourishment. Only on one occasion did I see a Cepobroticus carry a particle of the substratum to another spot, insert it and pat it down with her fore feet. When fresh fruit was introduced into the nest, it was much less frequently visited and eaten by the guests than by their hosts.
Brown observed a colony from near Manaus, Brazil (reported as silvestrii in Kempf and Brown 1968; reidentified as symmetochus by Brandao 1990). Brown reported "The colony ... was found in a small rotten log in rain forest on 26.VIII.1962, in a small chamber with a small species of Trachymyrmex. The ants of both species were found throughout the fungus garden of the chamber, but off to one side in a small chamber was found a group of the Trachymyrmex clustered with a small piece of fungus garden unoccupied by Megalomyrmex. ... the situation suggested that the M. silvestrii colony had successfully attacked and moved into the attine nest, and was in the process of plundering it."
Brandao (1990) reported a collection from Belem, PA, Brazil, from a nest of an unidentified Trachymyrmex.
At La Selva, alate queens and males have been collected at blacklights. Males and queens were common at the lab clearing blacklight on 4 Aug 1992. A lone worker was obtained by Ronald Vargas, during general collection of ants from trail surfaces and low vegetation.
Bolivia, Brazil, Panama, Costa Rica. Costa Rica: Atlantic lowlands.
Taxonomic history
Wheeler & Wheeler, 1955c PDF: 126 (l.); Boudinot et al., 2013 PDF: 63 (w.q.m.).See also: Brandão, 1990b PDF: 445.
Megalomyrmex symmetochus is a species of ant in the subfamily Myrmicinae. It is native to Panama.[1]
M. symmetochus was discovered by William M. Wheeler in late July 1924 in the fungus gardens of the attine Sericomyrmex amabilis of Barro Colorado Island.[2]
Workers are 3 to 3.5 mm long, with small, feebly convex eyes, that are probably adapted to living within the dark fungal gardens of their host. Very small ocelli are only sometimes present. Workers are yellowish red, with mandibles, funiculi, the posterior half of the first segment of the gaster and the sutures of the thorax and pedicels brown. The tip of the gaster is yellowish.[2]
The female is almost 4 mm long. She has larger eyes than the workers and distinct ocelli. Otherwise, they look very similar to workers. Each ocellus has a black margin internally. The wings are yellowish hyaline and iridescent, with veins and pterostigma pale yellow. The membranes of the wings are distinctly pubescent.[2]
Males are almost 3 mm long. They bear very large eyes and ocelli. Their body form is very similar to that of workers and females, but with smooth sides of the thorax. The wings have longer pubescence that in the female. Males are brownish yellow, with a little darker gaster and slightly paler antennae and legs. The eyes and a spot along the inner border of each ocellus are black.[2]
M. Symmetochus often live among and take from the gardens of fungus-growing ants, sometimes usurping the gardens.[3] In some populations they coexist with fungus-growing hosts>80% of the time.[4] They number their hosts as much as 1:3.[5] Young queens stealthily invade fungus-growing colonies and start their own lineage in the fungus garden.[6] Then, they clip the wings of the hosts' virgin queens, but not the males.[6]
When their hosts live near predators who destroy the nests and destroy their gardens, M. Symmetochus serves as protection of their host colonies. Hundreds of worker ants live throughout the nest of the host, and when invaders attack, individuals recruit the others inside to defend the nest. Also, these ants have been observed projecting their stings, leaving two isomers of 3-butyl-5-hexylpyrrolizidine, marking the nest with the scent of its toxin.[5] It seems that some species avoid nests with their marked scent. When there are no invaders, M. Symmetochus commonly have aggressive conflict with their hosts.[6] Therefore, it seems that when M. Symmetochus lives with a host with no outside danger, they serve as parasites, but when the hosts live near other threats, they have a mutualistic relationship with their hosts.[5]
Megalomyrmex symmetochus is a species of ant in the subfamily Myrmicinae. It is native to Panama.
M. symmetochus was discovered by William M. Wheeler in late July 1924 in the fungus gardens of the attine Sericomyrmex amabilis of Barro Colorado Island.
