Introduction
Almost all neotropical Theclinae species are placed in the Eumaeini. The tribe is not particularly well represented in collections, so until fairly recently a high percentage remained unstudied, and were inappropriately filed away in the ‘convenience’ genus Thecla. Many taxonomists have attempted to rationalise the systematics of the Eumaeini, the most recent being Robbins who published a revision in 2004, reclassifying the taxa into 83 genera. Currently there are 1058 known species. Taking into account their small size, secretive behaviour, and the great similarities between many species, it is estimated that about another 200 species probably remain to be discovered.
There are 9 Arcas species, found variously from Mexico to Bolivia and Argentina. All have metallic green undersides, frosted or peppered with black, and on most species there is a broad black band across the hindwing. All Arcas species have a pair of long twisted filamentous tails on the hindwings. On the upper surface the males are metallic turquoise, green or blue according to species, and have a broad suffused area of dark brown around the apex and wing margins. Females are usually more bluish on the upperside, and have a more rounded apex to the forewings.
Arcas tuneta is found on the Guyana Shield and on the eastern slopes of the Andes from Colombia to Bolivia. It also occurs in western Brazil.
Habitats
This species is found in rainforest and transitional cloudforest habitats at elevations between about 200-900m.
Lifecycle
To be completed.
Adult behaviour
Both sexes probably spend most of their lives in the canopy, however they have a strange tendency to suddenly appear ‘out of nowhere’, dropping from trees to settle on the leaves of saplings in dappled sunlight. At such times the hindwings of males are gyrated, drawing attention to the long filamentous tails. Females have a greater tendency to lie flat against a leaf, and do not normally gyrate their tails, although the slightest breeze is enough to make them wiggle and attract attention.