''Linepithema fuscum'' is a species of

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22 ...

in the genus ''

Linepithema ''Linepithema'' is a genus of small ants in the subfamily Dolichoderinae. Distribution Their native distribution rage from northern Mexico, east into the Caribbean, and south into northern Argentina. Two species have been spread around the w ...

''. Described by Mayr in 1866, the species is endemic to

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

. ''Linepithema fucsum'' was the first species-level name assigned to genus ''Linepithema'' by Mayr. It is related to ''L. angulatum, L. keiteli, L. piliferum and L. tsachila.'' However, only ''Linepithema fuscum'' remains without a worker association and it could be possible that males of ''Linepithema fuscum'' actually belong to the workers of ''L. angulatum.'' Little is known about ''Linepithema fuscum'' due to the scarcity of the collected samples.

Taxonomy

In 1866, Mayr first described ''Linepithema fuscum'' and 28 species-level names have been assigned to the genus ''Linepithema'' ever since. However, species limit within ''Linepithema'' is poorly understood and there haven't been efforts to synthesize the isolated description of the species into one coherent taxonomy. The description of ''Linepithema fuscum'' was initially based on a male species description by Mayr. Shattuck later cited the male morphology difference in his phylogenetic research to propose two different species groups of ''L.. fuscum'' and ''L. humile'' in the genus ''Linepithema.''

Distribution

''Linepithema fuscum'' is native to Argentina, Ecuador, Peru, and Venezuela. But they have been also found in the Colombian inter-Andean valley.

Description

Little is known about the biology of ''L. fuscum''. The species has been collected from 200 to nearly 3000 meters in elevation. One sample was collected from a "shrubby pasture" and another sample was collected inside a laboratory building in Madre de Dios in Peru. From the 2 samples, the researchers were able to determine the haploid chromosome number to be N=9 but could not find other differences.

Castes

Little is known about the caste system of ''L. fuscum.'' Similar to most ant species, the caste system consists of workers, male, and a queen.

Males

Compared to other species in the ''Linepithema'' genus, males of ''L. fuscum'' have a smaller, more rounded

propodeum The propodeum or propodium is the first abdominal segment in Apocrita Hymenoptera (wasps, bees and ants). It is fused with the thorax to form the mesosoma. It is a single large sclerite, not subdivided, and bears a pair of spiracles. It is strongl ...

with a straight to the convex posterior face. Furthermore, the wing venation pattern of the males is similar to that of the queens and consists of two elongate submarginal cells. This is in contrast to other males in the ''Linepithema'' genus which have only one submarginal cell. The volsella, a male reproductive appendage, is strongly extruding in ''L. fuscum'' males. The leg of the males is relatively short compared to other species (<70 mm). The head, body, and appendages of the male are medium brown in color.

Workers

Smaller in size. Some of the key characteristics useful for diagnosis of ''L. fuscum'' workers include sparse to absent metapleural pubescence, variable propodeal shape, 0-9 standing setae, and well-developed pre-sutural clypeal groove. The color of the body is medium brown to dark brown but mandibles, antennae, trochanters, and tarsi are somewhat lighter.

Queen

Moderately sized species (maximum mesosomal length: 1.87-1.91 mm). It is unknown if the queen has wings or not. Some of the key characteristics useful for diagnosis of the queen include mesoscutum with more than 10 standing setae, medium brown body color with lighter colored antennal scapes, legs, and mandibles.

References

Dolichoderinae Hymenoptera of South America Insects described in 1866 {{Dolichoderinae-stub