Butterflies of the Amazon and Andes
Sword-tailed Doctor
Rhetus arcius  LINNAEUS, 1763


subfamily - RIODININAE


Rhetus arcius, Satipo, Peru  Adrian Hoskins

Butterflies in the genus Rhetus are noted for their short palpi, and for having a beautiful blue sheen across the upper surface of the wings. Rhetus are closely allied to Ancyluris and have a similar wing shape. In Ancyluris however there is a blue iridescence on the underside of the wings, but not on the upperside.
There are 3 Rhetus species, of which periander is the commonest and most widespread. The others are dysonii, in which the pink markings on the hindwings are of a different configuration, and arcius which has much longer hindwing tails and in which the blue iridescence on the forewings is reduced.
Rhetus arcius is found from Mexico to Peru. There are 8 named subspecies.
Rhetus arcius, Pauti, Junin, Peru  Adrian Hoskins
Rhetus arcius is usually found singly in the vicinity of streams or ditches. It occurs in rainforest and cloudforest habitats at altitudes between 0-1200m, but is commonest between about 400-800m. The butterfly can be seen throughout the year.

Rhetus arcius, Satipo, Peru  Adrian Hoskins

The eggs are white, and laid singly on stems or leaf axils. The foodplants are Terminalia amazonica ( Combretaceae ) and Mabea occidentalis ( Euphorbiaceae ).

Rhetus arcius, Satipo, Peru  Adrian Hoskins

Adult behaviour

The butterflies have a very rapid and erratic flight. Males perch under leaves at a height of between about 3-8m above ground in the early morning. Later on, presumably after mating has taken place, they descend to ground level to imbibe at wet mud. After first they are very skittish and take flight instantly if disturbed, but after a few minutes they overcomes their nervousness and will sometimes remain in one spot for several minutes. Both sexes are attracted to Eupatorium flowers.

Rhetus arcius, Catarata Bayoz, Le Merced, Peru  Adrian Hoskins



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