Butterflies of
the Amazon and Andes
Social Skipper
Hyalothyrus neleus
LINNAEUS,
1758
Family - HESPERIIDAE
subfamily -
PYRGINAE
Tribe - EUDAMINI
introduction
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habitats |
lifecycle |
adult behaviour
Hyalothyrus neleus,
females, Rio
Alto Madre de
Dios, Peru
Introduction
The
genus
Hyalothyrus
comprises 5 known species, of which
neleus
is the commonest and most widespread.
It's vernacular name
Social Skipper is
given in recognition of it's habit of gathering in groups beneath leaves :
The
butterflies illustrated above were in a group of 7 discovered at rest beneath a large leaf in primary rainforest in southern Peru.
As our party of 4 butterfly photographers approached, the entire group burst into flight,
whizzing around our heads at high speed for 2 or 3 minutes. They returned one by
one over a period of several minutes until eventually 6 of them
had resettled under the original leaf. Making a second very
cautious approach one of our members was successful in capturing the image
below, which depicts 4 females and 2 plain brown males. We each
took turns to approach and photograph the butterflies but they were
incredibly nervous, and with each approach the numbers returning diminished
until only a single female remained.
Quite what was happening under this leaf is a mystery. Was it simply coincidence
that a mixed sex group of 7 Hyalothyrus neleus
happened to choose to roost under the same leaf ? It seems unlikely.
Communal roosting is not a unique phenomenon. The Monarch
Danaus plexippus is of course the most well known example - millions of
them overwinter together on pine trees in Mexico every year. Other
species which roost communally include the Migrant Sulphur
Phoebis sennae which commonly settles in groups of 50 or more on bushes in
Costa Rica, and the Common Longwing Heliconius erato
which I've seen roosting in clusters of up to a dozen at sites in Peru, Brazil
and Ecuador. In Britain the Silver-studded Blue Plebejus argus
often roosts in groups of up to 100 on heather bushes, and in
Venezuela I've seen as many as 40 Daggerwings Marpesia berania
clustered together under the leaves of trees.
The reason why these species gather in groups is unknown. With several million
leaves in the vicinity to choose from, why did the
Hyalothyrus neleus group settle beneath this particular one ? It seems
almost certain that a single butterfly initially settled there, and that
pheromones or visual stimuli then attracted the others. It is also very likely
that the same group of butterflies use this leaf for several days, and quite
possible that successive generations use it for weeks, or even months at a time.
Communal roosting may be a
defence strategy - there would be many more pairs of eyes, and more vibration
sensors ( found on butterfly legs ) to detect the approach of predators. The
sudden scatter-burst of the alarmed butterflies would certainly startle a bird,
and then the rapidly swirling mass of skippers, some with white patches, would
cause confusion and allow most to escape. A similar strategy is of
course used by zebras to evade attacking lions in Africa.
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Hyalothyrus neleus,
4 females and 2 males
( mage © Tony Hoare ) |
Habitats
This species is restricted to primary rainforest at altitudes between sea level and about 800
metres.
Lifecycle
The caterpillar feeds on Inga ( Fabaceae ) and is a
dirty greenish colour, with a series of prominent pale green spots along the
sides, and a large shiny reddish brown head. The internal organs and digestive
system are clearly visible through the translucent skin. I have no information
about the pupa, but in common with other Pyrgine skippers it is likely to be
dark and smooth, with the wing cases in a contrasting tone or colour.
Adult behaviour
Other than the communal roosting described above, the only other
observation I have relating to this species is the fact that it is
primarily active at dusk, or on overcast days.
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Hyalothyrus neleus,
female, Rio
Alto Madre de
Dios, Peru |
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