The prettiest Linepithema

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This post is about a real jewel of an ant.

Most myrmecologists know Linepithema for the pestiferous Argentine ant L. humile,  a small, brown, rather dull looking creature. The genus contains 18 other species, however, and not all are as drab. Check out Linepithema leucomelas:

Linepithema leucomelas (Paraná, Brazil)

This colorful ant is endemic to Brazil’s highly-endangered Atlantic coastal rainforest. I spent 6 years working on the taxonomy of this genus for my Ph.D., yet I never saw a living L. leucomelas until Mrs. Myrmecos & I traveled to Paraná in May. I’m not generally one to keep a life-list of ant sightings, but this was a species I was thrilled to find.

The nest site near Morretes, Brazil.

The nest occupied narrow spaces between dead leaves at the base of a bromeliad, as I’d expected from previous literature records. The ants’ unusual coloration may serve as a sort of camouflage. Individual workers were difficult to see against a mottled background, especially when moving. They appeared like sprightly little ghosts, while their various dark spots made discerning the head from the tail surprisingly hard.

Linepithema leucomelas (Paraná, Brazil)

While identification of L. leucomelas would seem straightforward from the color, the genus Tapinoma has produced a sympatric ant of similar patterning, Tapinoma atricepsThe latter species is stubbier, with the waist constriction concealed under the gaster, and the two ants smell differently when squished. Any ecological reasons underlying the apparent mimicry of the two species are unknown. As for most tropical insects, neither species has received scientific attention beyond the initial taxonomic description.

5 thoughts on “The prettiest Linepithema”

  1. Colourful? What does that mean? I live in a land where that ant is very dull (possibly because it’s very young or only forages at night, and even then most of its fellow night-foragers will be much more colourful).
    My question is really about relative terms in taxonomic descriptions: hairiness, shininess, relative proportions, colour (rarely mentioned).
    I ask because I’ve been looking at grasses today (Rhytidosperma aka wallaby grasses) and find the same problems: one taxonomist wrote or drew something and the next wrote/drew something else about the same species. And in those descriptions they use terms like ‘greatly exceeding’ which refer to some small character but fail to give the ordinary observer any sense of what the plant (or ant) might look like.

    1. You’ll find a treatment will sink or swim when you road test it with a lot of material. Rhytidosperma (formerly Austrodanthonia) taxonomy sits on the sliding scale of a) vague and b) continuous characters – usually involving the lemma (R. setaceum, caespitosum and R. acerosum are doozies for this). Best to check with type descriptions (if they are adequate) and the author’s concepts and match to herbarium sheets with a reliable determinavit. And spend a long time looking at variation. Eventually it may click. And you think Rhytidosperma is bad – Austrostipa and Eriachne are an order of magnitude worse.

  2. I sympathize, KMS, and I am one of those guilty of writing such obtuse stuff!

    Linepithema was once included in the genus Iridomyrmex, Greek for “rainbow ants”, referring to the nice colors of the Australian species that still remain in the latter genus. I think it amusing that Iridomyrmex humilis translated as humble rainbow ant, because of the irony that its colors are indeed humble, but its invasivess is anything but! Now in Linepithema, L. humile remains more humbly colored than than the ant that is the topic of this essay, rendering this one the beauty of the bunch – But, it’s all relative.

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