Butterflies of
the Amazon and Andes
Dull Brown Job
Nastra
chao
MABILLE, 1898
Family -
HESPERIIDAE
subfamily -
HESPERIINAE
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Nastra chao, Huacarpay, Cusco, Peru |
Introduction
There are at least 1038 known species of Grass Skippers ( Hesperiinae ) found
in the neotropical region, many of which are virtually 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 usually obscure, and it can be guaranteed that
there will be several dozen near identical species which can only be told apart by killing them and microscopically examining the venation and
genitalia. Because of these obstacles to identification most lepidopterists
ignore these species, and refer to them collectively and dismissively as "dull
brown jobs".
As a serious entomologist I always
endeavour to try and identify even the most obscure species. Even with a "dull brown job"
such as this there are a few clues that can provide pointers to a positive ID :- The antennae have noticeably
flattened clubs, and are strongly hooked at the tip. There is a 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 must also considerably narrow
the choice of candidates.
A contact in Colombia has suggested that the butterfly
might be Nastra chao, a species known to occur at
high altitudes in Peru and Bolivia.
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.
Habitats
This species was photographed nectaring at Senecio,
in arid scrubby terrain bordering the Huacarpay lakes near Cusco in Peru. At an
altitude of 3050m ( 10000ft ) the lakes are above the cloud layer and bathed in
sunshine for most of the year.
Lifecycle
Unknown.
The
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.
Adult behaviour
No
observations other than that the butterfly nectars at
Senecio, and holds its wings in the
typical Hesperiine posture when feeding and basking.
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