Butterflies of
the Amazon and Andes
Julia, or Flambeau
Dryas iulia
FABRICIUS, 1775
Family -
NYMPHALIDAE
subfamily -
HELICONIINAE
Tribe - HELICONIINI
introduction
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habitats |
lifecycle |
adult behaviour
Dryas iulia, Rio Pindayo, Peru
Introduction
The dazzling orange Julia is
widespread and common in the southern United States, and extends
south
through Central America and much of the Caribbean, and throughout
all of the tropical and subtropical areas of South America.
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In tropical
regions males of many species visit sandbanks, riversides and damp
paths to indulge in "mud-puddling". Their purpose is to imbibe mineralised water,
from which they obtain sodium and other minerals. They often
indulge in filter-feeding, whereby they rapidly and continually
pump water through their bodies while extracting these dissolved
substances.
It is common for males to squirt the filtered water onto the
ground and use it to dissolve more minerals from the sand or rock.
This water is then re-imbibed to extract further minerals. These
salts are later passed to females
during copulation, and are believed to be essential for the
production of fertile eggs. Males which have already mated return
to replenish their salts, and often mate again with another
female. Females do not normally mud-puddle, they feed instead on
nectar, visiting herbaceous plants and flowering trees.
On the sandbanks, typically just one or two males will chance upon
a suitable
feeding spot, but other butterflies flying past
seem able to recognise their brethren on the ground, and swoop
down to join them. The bright patch of colourful butterflies
quickly becomes a magnet to every passing male of the same
species, and after an hour or so hundreds or even thousands of
butterflies may assemble at certain particularly mineral-rich
sandbanks.
Normally
several different species are present at these feeding places.
It might be expected that the various species would be randomly
distributed on the ground but this is not the case. Each butterfly polarises very strongly towards it's own brethren, so that each species
congregates as a discrete group.
In calm weather the butterflies in each group are positioned
randomly, but on riverbanks there is usually a constant gentle
breeze, so all the butterflies in each group tend to face into the
breeze. In this way they are less likely to be blown about and
lose their feeding spot to a competitor.
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Habitats
The butterflies fly in
rainforest and deciduous forests, but are commonly encountered in disturbed open
habitats such as forest clearings, cattle pastures, along riverbanks, and in
flowery gardens.
Dryas iulia, Catarata Bayoz, Peru
Lifecycle
Like most other Heliconiines, the Julia lays it's eggs on
Passiflora
( Passion flower ). There has been a great deal of study into the relationship
between these plants and Heliconiine butterflies, which strongly suggests they they
co-evolved. There is a constant evolutionary battle in which the plants try to
defend themselves from the butterflies. Some
Passiflora vines
for example produce false stipules at the base of leaf stems, that induce egg laying
by certain Heliconiine species. A day or two later the stipules drop off, carrying the eggs with
them. Eggs which fall to the ground probably get eaten by ants, but even if they
survive, the resulting larvae will starve. Certain other Passiflora
vines produce tiny tubercules on the stipules that mimic Heliconiine
eggs. Any butterfly visiting the plant sees the false eggs, is misled into
thinking that the plant is already overladen with eggs, and is consequently
inhibited from ovipositing.
The
Julia lays it's eggs singly, on the tendrils and leaves of Passiflora
and Plectostemma,
or even on nearby vegetation, and is thus less specialised than most other
Heliconiines. Perhaps as a consequence it is far more common and widespread than most
other members of the subfamily.
The
body of the multicoloured caterpillar is adorned with long black thorny spines,
with a further pair arising from the head. It feeds openly in the daylight.
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Dryas iulia, Rio Madre de Dios, Peru |
Adult behaviour
Males often gather in small groups to drink at damp mineral-rich
sites such as salt-licks, sandbanks, peccary wallows, or
urine-soaked earth. They are also regularly observed sipping
liquid from the corner of the eyes of the yellow-throated caiman
in Brazil, or from the eyes of turtles in Peru !
Females behave differently, visiting flowers including
Lantana,
Eupatorium and various canopy
species, but as well as drinking nectar they feed on dissolved
pollen, from which they obtain nutrients that have been shown to
be essential to egg production.
I have not
observed the courtship, but in Costa Rica have found mated pairs
resting on low foliage with wings closed, in early afternoon. When
copulated the butterflies are very reluctant to fly.
Dryas iulia, Catarata Bayoz, La Merced, Peru
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