Introduction
The Pyrginae, popularly known as Flats or Spreadwings, are a cosmopolitan subfamily distributed across temperate and tropical habitats throughout the world. In the Americas there are 990 species.
About 580 species are placed within the tribe Pyrgini.
The genus Sostrata is closely allied to Pythonides, Eracon and Quadrus. These genera comprise a total of about 45 small species, characterised by having a series of tiny transparent marks on their forewings, and a peppering of metallic blue scales overlaid on a dingy brown ground colour.
Sostrata pusilla is distributed from Nicaragua to Bolivia. There are 2 subspecies – pusilla rangers from Nicaragua to northern Ecuador, while pulsa occurs in southern Ecuador, Peru and Bolivia.
Habitats
This species occurs in rainforest and cloudforest habitats at altitudes between about 200-1000m.
Lifecycle
The lifecycle appears to be unrecorded. Generally, Pyrgine butterflies lay their eggs singly on either the upperside or underside of leaves.
The caterpillars are typically dull green or brownish, with thin longitudinal lines along the back and sides, and with black shiny heads. They feed typically on low growing herbaceous plants, but some feed on the leaves of bushes or trees. The pupae are usually dark and smooth, with the wing cases in a contrasting tone or colour. They are normally formed within silken tents formed by spinning together the leaves of the foodplant.
Adult behaviour
The butterfly is usually encountered as solitary males. They are active mainly in the early afternoon when they can be seen basking on foliage or logs.