Butterflies of the
Amazon and Andes
Dull Brown Job
Family - HESPERIIDAE
Nastra chao, Huacarpay, Cusco, Peru ©
There are over 1040 species of Grass Skipper ( Hesperiinae ) found
in the neotropical region, many of which are almost impossible to
identify from photographs. A great many of them are dark brown in
colour, and unmarked. Even if they do have markings these are often
obscure, and there will be several dozen near-identical species
which can only be told apart by microscopically examining the
genitalia. Because of these obstacles to identification most
lepidopterists ignore these species, and refer to them collectively
and contemptuously as 'dull brown jobs'.
Nevertheless there are always a few clues that can provide pointers
to a positive ID. The butterfly depicted above for example has
antennae with noticeably flattened clubs that are strongly hooked at
the tip. Another clue lies in the series of vague pale or
semi-hyaline dash-shaped markings abutting the costa of the
forewing. The high altitude at which the butterfly was found also
considerably narrows the choice of candidates.
There are 11 species in
the genus Nastra, 3 of which occur in
the southern United States, while the remainder are distributed
variously from Mexico to Bolivia and Argentina.
Nastra chao is found in Peru and Bolivia.
This species inhabits arid scrubby terrain at elevations between
eggs of other Nastra species, are
typically whitish or straw coloured, and laid singly on grass
blades. The larvae, in common with those of most other Hesperiine
skippers almost certainly shelter by day within a silked tube at the
base of grasses, and emerge at dusk to feed on a variety of grasses
( most Hesperiine larvae progress from finer grasses to coarser
species as they mature ). They are likely to be greenish in colour
with fine longitudinal lines and will possess caudal prongs - a pair
of short anal projections that are used to flick the droppings clear
of the feeding site.
observations other than that the butterfly nectars at
Senecio, and holds its wings in the
typical Hesperiine posture when feeding and basking.