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Frequently Asked
Questions
Can hawkmoth
caterpillars sting with their horn ?
horn on tail of Privet Hawkmoth
caterpillar
Sphinx ligustri ©
Adrian Hoskins
All
Hawkmoths ( Sphingidae ) throughout the world have
caterpillars that are equipped with a horn at the tail end.
In some species it is short and may be curled like a pig's
tail, while in others it can be extremely long - almost as
long as the caterpillar itself !
These horns look sharp and
dangerous but are in fact quite soft to touch. They cannot
sting and are entirely harmless. The purpose of the horns is
apparently unknown and would make a fascinating subject for
a scientific study.
Are any caterpillars
dangerous to touch ?
Drinker moth larva
Euthrix
potatoria
- its hairs cause mild itching ©
Adrian Hoskins
There are over half a million species of
caterpillar in the world, and most are completely harmless
to touch. Some however, particularly those in the families
Megalopygidae, Saturniidae, Lymantridae and Lasiocampidae
have hairs or spines which can irritate or sting. In Europe
the most well known example the Brown-tail moth
Euproctis chrysorrhoea. The
larval webs of this moth are commonly found on hawthorn and
bramble, particularly in coastal areas of southern England.
The caterpillars shed their hairs easily, and if these
become airborne and find their way into human eyes they can
cause painful inflammation.
Automeris liberia ( Saturniidae
), Peru - its spines can deliver a painful sting ©
Adrian Hoskins
There are also many species of Saturniidae e.g.
Automeris liberia whose
caterpillars are adorned with dozens of stinging spines,
each shaped like a miniature Xmas tree. In most cases the
sting is no worse than that of a nettle plant, but in
at least one species it can be lethal :
The well camouflaged spiked
caterpillars of Lonomia obliqua
are often found clustered in groups of up to 100 on the
trunks of trees in Amazonia. There have been many incidents
where people have
unwittingly
touched or rubbed their arm against groups
of these caterpillars that were
gathered on tree trunks. The
effects of a dose from multiple caterpillars can be
very severe, including massive
intercranial
haemorrhaging and kidney failure.
Lonomia obliqua
caterpillars are a frequent cause of death in southern
Brazil - 354 people died between 1989 and 2005. The fatality
rate is about 1.7% - roughly equivalent to that of
rattlesnake bites.
If in doubt
keep well away from spiky caterpillars!
Do
some moths have feathers instead of wings ?
Many-plumed moth Alucita hexadactyla ©
Adrian Hoskins
In a manner of speaking,
yes. Most moths
have 2 pairs of
overlapping wings, each comprised of a very thin double
membrane with rigidity supplied by a network of tubular
veins that radiate from the base of the wings.
The Plume
moths ( Pterophorinae ) and Many-plumed moths
( Alucitidae ) however have no wing membranes.
Instead their fore and hind wings each consist of feathery
plumes - rigid spines from which branch dozens of long thin
plume-like scales.
There are 186 known species of Alucitidae worldwide, many of
which have only been discovered in the last 20 years. The
name of the moth illustrated above,
hexadactyla translates as
'20
fingers'
and is a misnomer as the moth actually has 24
'feathers',
although some are hidden from view.
Which
layer of the rainforest do butterflies live in ?
Butterflies
live at all layers in the rainforest.
Some species never fly more
than about a foot above the ground. Others live permanently
at the top of the tallest trees. A myriad of other species
live in the various layers in between. There are also many
species which normally live in the tree tops but sometimes
come down to ground level at
"light gaps" where sunlight penetrates to the forest floor.
Why
do male butterflies emerge before females ?
In species
which overwinter as adults, e.g. the
Brimstone, it is noticeable
that males awaken from hibernation about 2 or 3 weeks before
the first females appear. The probable reason is that prior
to copulation the females are very sedentary - it would be
wasteful for them to fly until after they have mated, and
would expose them to the risk of predation unnecessarily.
Males on the other hand need a few days beforehand to feed
up on flower nectar and build up their food reserves, giving
them the energy to enable them to fly all day in search of
potential mates.
In species
that emerge from the chrysalis in spring and summer, e.g.
the
Swallowtail, the males
emerge on average about a week before the females. The
reason for this is that females lose their attraction to
males very quickly, probably because the strength of their
pheromones diminishes with passing time. Consequently they
must mate within a day or two of emergence, so nature
ensures that there are plenty of males already available for
the females when they emerge.
Why do butterflies
gather at sandbanks and mud ?
Butterflies
seen on sandbanks or imbibing moisture from muddy patches
are almost always males. They home in on sources of sodium
and nitrates which are found dissolved in mud or damp sand.
This process is commonly called
'mud-puddling'.
Sodium is vital for physiological functions including
digestion, reproduction and flight. Urine-soaked ground,
carnivore dung and bird droppings are especially rich in
these minerals, and can attract large aggregations of males.
Males usually mate with more than one female, so after
mating they need to puddle again to replenish lost salts.
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.
Females do not
normally
'mud-puddle',
they feed instead on nectar, fallen fruit and other organic
matter. They obtain their sodium in a different way.
It is
passed to them along with spermatophore, by the males during
copulation. Females therefore do not need to waste valuable
time puddling, and can instead concentrate on searching for
good oviposition sites.
Phoebis argante and Rhabdodryas
trite. Males aggregating at Satipo, Peru ©
Adrian Hoskins
Protesilaus earis, Madre de
Dios, Peru ©
Adrian Hoskins
How long ago did
butterflies evolve ?
Estimates of the age of the earliest insect fossils date
back to at least 300 million years ago ( MYA ). The earliest
Lepidoptera ( butterflies, moths and skippers ) are
generally supposed to have evolved from the Trichoptera (
caddis flies ) somewhere in the region of 140-200 MYA, at
roughly the same time as the appearance of the first
flowering plants. At one time, the land masses of the Earth
were divided into 4 continents - Laurentia, Baltica, Siberia
and Gondwanaland. They gradually converged, and about 350
MYA became linked to form the super-continent Pangaea.
Butterflies
and other insects probably originated on Pangaea, which then
began to break up about 130 MYA, ultimately forming the
present day continents.
The species
which first appeared on Pangaea have long been extinct, but
nevertheless many of the genera and species flying today
have been in existence for millions of years - the South
American genus Brassolis for
example
first evolved in the late Eocene Period,
about 40 million years ago.
More information on this
subject can be found in the
Evolution section.
Prodryas
persephone ( Nymphalidae )
SCUDDER, 1878.
This is one of a dozen species of butterfly found in the
Florissant fossil beds, Colorado, USA. It dates from
the Oligocene period, 30 million years ago.
Image supplied.
How high can butterflies
fly ?
The highest flying
butterfly known is the Satyrine
Paralasa nepalica, discovered by
PAULUS
in 1983. The butterfly is found at altitudes as high as
4500m ( 14800 ft )
in
Shey Phoksundo national park in Nepal. Another
butterfly, the Uncompahgre Fritillary
Boloria improba acrocnema, spends its entire
lifecycle at altitudes between 4000-4200m in the San Juan
mountains of Colorado, USA, although other subspecies breed
at lower altitudes in Canada. Perhaps even more amazing
however is the Painted Lady Vanessa
cardui which is found in almost every region of the
world in habitats ranging from
deserts to
rainforests, prairies and tundra,
and has been recorded at altitudes between sea level and
4000m !
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Paralasa nepalica ( Satyrinae )
PAULUS, 1983 |
What are frass-chains ?
Frass chains
are constructed by many caterpillars, chiefly neotropical
and Afro-Asian Nymphalidae. When not feeding, the young
larvae rest at the tip of a chain constructed from their
own droppings. The larva typically eats away the leaf
tissue, leaving only the midrib intact, and then deposits
a row of its droppings along the midrib. The droppings are
bound together with silk. The line or
'chain'
of droppings ( frass ) is then extended so it projects by
about 2 centimetres beyond the leaf tip.
The theory
is that it is a defence strategy to protect tiny larvae
from marauding ants – observations by Phil DeVries for
example indicate that ants are unwilling to walk out on
the
'tight-rope'
to attack larvae. This may be because they cannot grip it
properly to walk on, or possibly because the frass
contains a toxin that deters them. The latter might also
explain why larvae of many micro moths camouflage
themselves with their droppings,
rather than decorating themselves with fragments of
leaves.
Where did the Purple
Emperor's name originate ?
In the British colonial
era butterfly collecting was a popular Pastime for army
officers, who invented English names for their captures.
It became traditional to name insects after army or naval
ranks or sovereign titles. Hence there are moths such as
the Golden Emperor, and butterflies including the
Archduke, Monarch, Commodore, Black Prince, Commander,
Chocolate Soldier, Baron, Palm King, Lance Sergeant, Tawny
Rajah and Queen Alexandra Birdwing.
The Purple Emperor
butterfly however was named by Moses Harris in 1766. The
reason for its name was probably simply a reference to
it's magnificence - it is one of the largest and most
highly prized butterflies in Europe. The name could also
be connected to the fact that the male Purple Emperors
habitually perch on clumps of leaves, known commonly as
"thrones" at the top of high oak trees. They use these
perches as lookout posts from which to sight and intercept
females. It is common to see groups of males engaged in
aerial dog-fights, competing for the best "throne"
position.
Purple Emperor Apatura iris,
male, Hampshire, England ©
Adrian Hoskins
Why do some butterflies
have hairy eyes ?
All
butterflies in the genus Lethe
( Satyrinae ) have a dense layer of fine bristles or
' hairs'
on their compound eyes. My observations
of various Lethe species in
Sri Lanka, Borneo and West Malaysia indicate that the
adults are strongly attracted to wet dung and spend long
periods probing into it, at which times their heads push
right into the substance. It seems possible therefore that
the 'hairs' may function in the same way as a cat's
whiskers, acting as tactile sensors which warn the
butterfly if their eyes get too close to the dung, which
would almost certainly blind them if it
adhered
to the surface of the eyes.
Bear in mind however that
not everything in nature has a purpose or reason. It could
simply be the case that the hairs first appeared as a
random mutation that was neither beneficial or harmful,
and consequently there would be no natural selection
pressure for it to
'breed
out'
and revert to a non-hairy eye.
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