Meliboeus Swordtail
Ancyluris meliboeus
The Meliboeus Swordtail is small enough to fit comfortably in the palm of a hand, but its wings don't seem particularly interested in appearing small. Black is cut through with vivid red, the hindwings trail into two fine tails and, in males, a shift in angle can bring an unexpected blue green sheen into view.
That last colour is easy to miss. Look straight at a specimen and the wings may appear predominantly black and red. Move it towards the light and metallic colour begins appearing across the underside. Move again and some of it disappears. At around 40 mm across, Ancyluris meliboeus doesn't need much size to put on a rather good display.
Classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Riodinidae
Subfamily: Riodininae
Genus: Ancyluris
Species: Ancyluris meliboeus
Common Name: Meliboeus Swordtail
Distribution: Tropical South America
One of the Metalmarks
Ancyluris meliboeus belongs to Riodinidae, the metalmark butterflies. The family is especially diverse through the tropical Americas, and appearances vary enormously. Some species are fairly subdued. Others seem to have taken the name metalmark as a challenge.
Ancyluris sits comfortably in the second group. Members of the genus can combine dark wings with vivid bands, metallic colour and elongated hindwings, giving relatively small butterflies surprisingly elaborate silhouettes.
Several subspecies of A. meliboeus have been described across its South American range. Their markings can vary, so locality becomes useful when trying to take an identification beyond species level. A butterfly may carry clues to where it came from, but provenance is considerably more reliable than asking the wings to provide an address.
Blue That Won't Sit Still
The upper wings make the most immediate impression. Deep black to brown black is interrupted by strong red markings across both pairs of wings, while the hindwings narrow into those characteristic tails.
Then the light moves.
Particularly in males, the underside can reveal brilliant blue to blue green iridescence. This isn't simply blue pigment painted across the scales. Microscopic structures interact with incoming light, strengthening particular wavelengths at some viewing angles and weakening them at others. The result is structural colour.
It's why photographs of the same butterfly can look oddly inconsistent. One captures brilliant blue. Another makes it look as though most of that colour was never there.
A preserved specimen still does it. The butterfly has stopped moving, but the colour hasn't.
Somewhere Beneath the Canopy
The Meliboeus Swordtail occurs across tropical South America, with records including Brazil, Suriname, Colombia, Peru and Bolivia. Its range includes humid tropical forest environments across parts of Amazonia and areas associated with the eastern Andes.
Adults are active during the day. Males may visit damp ground and other places where dissolved minerals can be obtained, a behaviour known from many butterfly groups.
The earlier stages are less conspicuous. Like other butterflies, A. meliboeus undergoes complete metamorphosis, passing through egg, larva and pupa before the winged adult appears.
Riodinid caterpillars are particularly interesting because relationships with ants occur throughout the family. In some species, larvae possess specialised structures and produce secretions involved in these interactions. The arrangement varies considerably between metalmarks, though, and the detailed life histories of many tropical species aren't as well documented as their adult appearance. A. meliboeus is a good place not to fill the gaps with what one of its relatives happens to do.
A Swordtail Without the Swallowtail
Long hindwing tails immediately suggest swallowtails. The common name doesn't exactly discourage the comparison.
The Meliboeus Swordtail isn't one. True swallowtails belong to Papilionidae, while A. meliboeus sits within Riodinidae. Similar elongated wings have appeared in separate branches of butterfly evolution, so a conspicuous resemblance doesn't necessarily indicate close relationship.
Tails can be useful as well as decorative. In some butterflies, hindwing tails and nearby markings appear to misdirect attacks towards the rear of the wings and away from the more vulnerable head and body. A predator taking the end of a wing is a considerably better outcome for the butterfly than one finding its thorax.
That doesn't mean every tailed butterfly uses precisely the same defensive trick. It does make the Meliboeus Swordtail a useful reminder that one dramatic feature rarely tells you where a butterfly belongs.
A Butterfly That Changed Its Name
Johan Christian Fabricius described the species in 1777 as Papilio meliboeus. That placement looks strange beside its modern classification until you look at what Papilio once contained.
Early taxonomists placed a very broad assortment of butterflies within the genus. As more species became known and their differences were studied, those enormous early groupings were divided into smaller ones. Meliboeus eventually found its place within Ancyluris and among the metalmarks.
Older names haven't vanished completely. They remain in historical literature, museum records and old specimen labels.
On a preserved insect, that can become interesting in its own right. The animal hasn't changed at all. The little piece of paper underneath it might reveal how our understanding of the animal has.
In the Apotheca
Spread flat, the Meliboeus Swordtail gives away most of its obvious features at once. Red cuts sharply across the black upper wings and the two tails carry the silhouette beyond the main body of the butterfly.
The blue asks for more effort.
A specimen can sit quietly in its frame looking almost entirely black and red until the viewing angle changes. Then metallic blue green appears where there seemed to be none. Walk a little further and it retreats again.
For a butterfly only around 40 mm across, Ancyluris meliboeus has managed to fit quite a lot into its wings. Some of it just refuses to appear all at once.
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