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Taxonomy & Evolution
1 - Taxonomy
2 - Butterfly Families and
subfamilies
3 - What is a species / subspecies ?
4 - Evolution and Speciation
5 - Lepidoptera and the Evolutionary
table
6
- Butterfly World Census
Taxonomy
- the classification
of organisms by presumed relationships
The Linnaean System
Before the advent of scientific nomenclature, confusion reigned :
Example 1 - The
butterfly known in Britain as the Camberwell Beauty has in past
times been called the Grand Surprise, the
Willow Beauty and the White Petticoat. In the USA it is called the
Mourning Cloak. In Europe it has common names in several different
languages.
Example 2 - The two
butterflies known to early entomologists as the Selvedged Heath
Eye and the Golden Heath Eye were later discovered to be the male
and female of a single species which was initially called the
Gatekeeper but is now called the Small Heath. The original name
Gatekeeper is now applied to an entirely different species which
has variously been known as the Hedge Brown, Hedge Eye and Large
Heath. The name Large Heath however is now used for an entirely
different species that was previously known as the Manchester Argus,
or Marsh Ringlet !
The Swedish naturalist Carl von Linné ( Carolus Linnaeus )
decided
to put an end to this confusion. He realised that an
internationally recognised name was needed for every creature and
plant, and that every organism should be classified according to
it's relationship with other organisms.
In 1735 he launched the Systema Naturae, a catalogue of the names of
all known animals and plants. Later, in 1758 came the 10th edition
of Systema Naturae, which is regarded as the starting
point for the current system of classifying animals and plants by family, genus and
species.
Originally Linnaeus placed all butterflies and moths in the same
genus Papilio. Later it was realised
that there was a need to divide this genus, so as to distinguish
groups with different characteristics.
Since the time of Linnaeus many thousands of new species have
been discovered and described by scientists, and hundreds of
genera have been created to accommodate them.
Every known taxon is
designated a binomial ( two-word ) name derived from Latin or
Greek roots. An example is the Common Blue butterfly
Polyommatus icarus :
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The Common Blue was
designated by Rottemburg in 1775 as
Polyommatus icarus. The first part of the name
means 'many spotted'. It
refers to the distinctive markings on the underside of the wings of all
species in
the genus
Polyommatus.
The name icarus
refers to a character in Greek Mythology.
According to legend Icarus and his father Daedalus were
imprisoned in the Labyrinth with a terrible creature, the
Minotaur. In order to escape, Daedalus fashioned a
pair of wings for himself and his son, made of feathers
and wax. Before they took off from the prison, Daedalus warned his
son not to fly too close to the sun. Icarus unfortunately
became so overcome by the
excitement of being able to fly that
forgot his father's warning. He got too close to the sun
and his wings melted. He
then fell into the sea in the area
which now bears his name, the Icarian Sea near
Icaria, an island southwest of
Samos.
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Common Blue,
Polyommatus icarus showing the
"many-spotted" underside.
Scientific names
should always be written with the genus, species
and subspecies italicised, then the author's name and the date the
description of the taxon was first published.
Thus the Common Blue
is called :
Polyommatus icarus icarus
ROTTEMBURG, 1775
The taxonomic
hierarchy
The Linnaean System divides the Animal Kingdom into groups
called phyla.
The phylum Arthropoda i.e. those animals with jointed limbs and a hard
exoskeleton, is divided into several classes. Among these are the Crustacea
which includes crabs,
lobsters, shrimps & woodlice. Other classes include Chilopoda
( centipedes ),
Diplopoda
( millipedes ), Arachnida ( mites, spiders & scorpions ) and the
Insecta ( insects ).
The
class Insecta includes over 75% of all animal species. It is divided into
several super-orders, one of which is Amphiesmenoptera. The latter
is split into 2 orders - Trichoptera (
caddisflies ) and Lepidoptera ( butterflies & moths ). These 2
orders share a common ancestor, Necrotaulidae, and have many
features in common, e.g. their wing venation is fundamentally
similar, their wings are covered in setae ( modified to form
scales in Lepidoptera ), and their larvae have mouthparts with
structures and glands modified to produce silk.
The table below shows
Polyommatus icarus in relation to the rest of the Animal Kingdom :
|
Kingdom |
Animalia |
Animals |
|
Phylum |
Arthropoda |
Joint-limbed invertebrates |
|
Class |
Insecta |
Insects |
|
Sub-Class |
Endopterygota |
Insects
with a 4 stage lifecycle : ova / larva / pupa / imago |
|
Superorder |
Amphiesmenoptera |
Trichoptera ( caddisflies ) & Lepidoptera |
|
Order |
Lepidoptera |
Butterflies, moths & skippers |
|
Sub-Order |
Ditrysia |
A division based on genitalia
characteristics |
|
Super-Family |
Papilionoidea |
Scudder butterflies |
|
Family |
Lycaenidae |
Gossamer-winged butterflies |
|
Sub-Family |
Polyommatinae |
Blues |
|
Tribe |
Polyommatini |
Ciliate Blues |
|
Sub-Tribe |
- |
no sub-tribe has been allocated
for the genus Polyommatus |
|
Genus |
Polyommatus |
Many-spotted Ciliate Blues |
|
Sub-Genus |
- |
no sub-genus has been allocated
for the species icarus |
|
species |
icarus |
Common
Blue |
|
subspecies |
mariscolore |
Irish sub-species of
icarus |
|
Author |
ROTTEMBURG, 1775 |
the taxonomist who
described the species |
Lepidoptera
About 7% of all life forms on Earth are members of the Order
Lepidoptera - the butterflies, skippers and moths ( indicated
in orange ) :
The
Lepidoptera comprises of about 150,000 known species ( this only
represents a fraction of the species in existence, as many more
await to be discovered and described, especially among the
tropical "micro" moth families ). The classification of
Lepidoptera is under constant revision, but they are currently
divided into 125 families, 6 of which are colloquially known as
butterflies :
|
Family |
subfamilies |
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Hesperiidae |
Heteropterinae, Hesperiinae,
Pyrginae, Pyrrhopyginae, Megathyminae, |
|
|
Coeliadinae, Trapezitinae |
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Papilionidae |
Papilioninae, Parnassinae,
Baroniinae |
|
Pieridae |
Pierinae, Coliadinae,
Dismorphiinae, Poritiinae, Miletinae, Lipteninae, Liphyrinae |
|
Lycaenidae |
Lycaeninae, Polyommatinae,
Theclinae, Curetinae |
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Riodinidae |
Riodininae, Euselasiinae |
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Nymphalidae |
Nymphalinae, Satyrinae,
Morphinae, Charaxinae, Apaturinae, Limenitidinae, |
|
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Biblidinae, Cyrestinae,
Heliconiinae, Danainae, Libytheinae |
Butterflies by day and moths
by night ?
It is wrong to think of butterflies and moths as being different. The families which we
call butterflies are generally those
with brightly coloured day-flying species.
There are however
hundreds of moths among the families Zygaenidae, Arctiidae
and Uraniidae which are also brightly coloured and day-flying.
Conversely there are many
butterflies among the Hesperiidae, Satyrinae and
Brassolini that are very dull and inconspicuous, and would be dismissed
as moths by most people.
Another "fact" often quoted is that
butterflies always have clubbed tips to their antennae, but that
moths never do. The colourful day-flying Zygaenidae moths however
do have swollen tips to their antennae, and the huge day-flying
Cane-borer moths ( Castniidae ) possess
clubbed antennae just like those of butterflies!
Perhaps
even more surprising is the fact that many butterflies fly at
night as well as during the day, particularly in the tropics. Examples include the
Caligo Owl butterflies,
Melanitis Evening Browns and certain Riodinids.
Examples from temperate regions include the Red
Admiral Vanessa atalanta and the
Monarch Danaus plexippus both of which
regularly fly into moth traps in the middle of the night.
Taxonomic revision
Taxonomy
is not an exact science. It relies on suppositions about the
relationships between various species, and about their
evolutionary ancestry. Because of this, the classification
( and
the scientific names ) of butterflies and moths are under constant revision.
New techniques such as microbiology, phylogenetics, DNA
sequencing, and the study of larval morphology regularly shed new
light on the relationships between species. This increasing
knowledge regularly results in the necessity to revise
classification. Sometimes it is a simple matter of relocating a
species to a different genus. On rare occasions however it may
require that a genus, tribe or even an entire subfamily be
migrated from its familiar home and relocated into another family
or superfamily.
The
inexact nature of taxonomy, and the fact that it relies on opinion
rather than fact, unfortunately means that scientists often find
themselves in disagreement about which genus a particular species
belongs to, or whether two or more butterflies with very similar
characteristics should be classified as separate species or as
subspecies.
Occasionally a taxonomist will believe that he or she has
discovered a "new to science" species and will describe it's characteristics and publish
a name for it. Later however they may realise that the species has already been described and
named by someone else. In such
cases the oldest name takes precedence, and the newer name is
discarded, and listed as an invalid ( junior ) synonym.
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The
reclassification of
Bia actorion
As our
knowledge grows and relationships between different taxa are more
clearly understood it sometimes becomes necessary for a butterfly
to be reclassified under a different genus, or even under a
different subfamily or family.
One of the most well known examples of this phenomenon is Bia
actorion, a neotropical species originally described by Linnaeus in 1763 as Papilio
actorion and placed
in the then all-embracing family Papilionidae. During the next
few years as many more species were discovered it became
clear that a single genus was inadequate. It was ordained that the original genus Papilio
should be used exclusively for Swallowtail butterflies, and that
new genera would need to be created to house all other species.
Consequently in 1819 Hübner created the
genus
Bia to
accommodate actorion. Hübner believed
that actorion was related to the "Browns" of Europe, so he placed
Bia
in the Satyridae, which was then regarded as a family of equal rank
to the Nymphalidae.
In the 20th century
Wahlberg and other taxonomists
concluded that the Satyridae,
Brassolidae, Amathusiidae, Acraeidae, Heliconiidae etc all shared a
number of common characteristics, and that they should thus all be
relegated to become subfamilies of the Nymphalidae.
For a few years Bia
actorion - also known
for a while as Napho
actoriaena - was
retained in the Satyrinae, but further studies
determined that it really belonged to the Brassolinae.
Currently Bia
actorion and it's
close relative Bia peruana are classified as members of the subtribe Biina, which is placed in
the Brassolini - a tribe within the Morphinae, which is now
considered to be a subfamily of the greatly enlarged
Nymphalidae !
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Bia actorion, Manu Biosphere Reserve, Peru
How scientists
describe and name new species
When someone thinks they've discovered a new species, they have to
provide sample specimens to taxonomists for analysis. By
comparing the structure of the
wing venation, genitalia and various other anatomical features
to that of currently known species, taxonomists can then easily
ascertain the genus, and decide whether the specimens represent
a previously known species or a new one.
If there are significant differences between
the new species and all previously known species it may be
regarded as sufficiently unique to deserve the creation of a new
genus. If on the other hand its anatomy is close to that of other species it will be placed in an
existing genus, and will be allocated a new species name
in recognition of its uniqueness.
New species are
given a Latinised name and a full scientific
description, which are published in a recognised scientific
journal such as Nature or New Scientist.
The origin of scientific names varies
enormously. Some species are named after Greek gods, some are
named after the place where the butterfly was discovered or
named in honour of some eminent entomologist. Names can also be
descriptive of the colour, pattern or wing shape.
The
Charismatic Metalmarks
Taxonomists are not usually renowned for having a great sense of
humour, but amongst their more hilarious moments they have
colluded to provide us with some entertaining scientific names. Hence
there are a pair of metalmarks from Colombia, named by Hall &
Harvey in 2002 as
Charis ma
and
Charis matic. Both have now been renamed rather less attractively as
Detritivora ma
and
D. matic.
The new genus name refers to the fact that the larvae feed
on decaying leaves and other detritus on the forest floor.
The world's
most dismal butterfly ?
Sometimes it can be difficult to think
up names for some of the more mundane looking species,
particularly for the hundreds of near-identical dull brown skipper
species found in the neotropics. In 1997 Austin was apparently so
totally unimpressed with his latest discovery that he gave a new Mexican
species the unfortunate name Inglorius
mediocris, which needs little translation !
Below is an example of a
scientific description :
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Inglorius
Austin, new genus
Type species:
Inglorius mediocris
Austin, new species
Description.
Palpi slender, third segment straight, protruding well
beyond second segment, about equal to length of dorsal
edge of second segment; antennae long, extending beyond
end of forewing discal cell, nearly 60% length of forewing
costa, black with pale ochreous beneath distad and below
club; club just over 1/4 (28%) antennal length, bent to
apiculus at thickest part, apiculus length about 2x club
width, nudum grey, of 12
segments (3 on club, 9 on apiculus); forewing discal cell
slightly produced, 75% length of anal margin, origin of
vein CuA2 nearer to CuA, than to wing base, hindwing
discal cell just over 1/2 wing width; mid tibiae with four
fine spines on inner surface and single pair of spurs,
hind tibiae with two pairs of spurs; forewing produced
with slight concavity between CuA! and 2A; hindwing convex
anteriorly, somewhat concave between CuAj and 2A; no
apparent secondary sexual characters. Male genitalia with
short tegumen; uncus longer than tegumen, undivided, and
hood-like over gnathos; gnathos
as long as uncus, divided, extending laterad of uncus in
dorsal view and as rectangular flaps mesad in ventral
view; vinculum sinuate; saccus short; valva very long,
ampulla/costa long and sloping somewhat downward caudad,
harpe long, roughly triangular ending in an inward turned
point caudad, dorsal margin undulate, weakly serrate
cephalad; aedeagus tubular (anterior portion missing),
caudal end expanded terminally in lateral view, no
apparent cornutus. |
More
'creative' species names
The
entomologist Burns was
clearly having a mental block when it came to naming his new
skipper - Cephise nuspesez (
pronounced "new species" ). Just to prove that weird humour
is not confined to entomologists, here are some of
the equally odd scientific names given to other creatures :
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Abra cadabra |
a species of clam - with magical
properties ? |
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Agra vation |
an "aggravating" carabid beetle |
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Cyclocephala nodanotherwon |
a species of scarab beetle - "not
another one !" |
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Heerz lukenatcha |
a species of braconid wasp - "here's lookin' at ya !" |
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Kamera lens |
a protozoan - shaped like a
"camera lens" |
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Pulchrapollia |
an extinct parrot, translates as
"Pretty Polly" |
The above show
both creativity and humour, but in 1969 when Spencer had the task
of inventing names for new flies, he invented possibly the most
boring series of species names in existence, by naming his
discoveries sequentially, as
Ophiomyia prima, secunda,
tertia, quarta, quinta, sexta,
septima,
octava, nona, undecima,
and duodecima
( Latin for "first", "second",
"third", etc. )
Dybowski went to the
opposite extreme when he proposed the ludicrously unpronounceable name
Gammaracanthuskytodermogammarus
loricatobaicalensis
for a new Amphipod
in 1927. It would have been the world's longest scientific name,
but luckily common sense prevailed and the name was rejected by the International Commission for Zoological
Nomenclature.
The honour of having the longest
scientific name actually approved by the ICZN actually goes to a species of
Stratiomyid fly -
Parastratiosphecomyia stratiosphecomyioides.
The shortest appears to be that of a Vespertilionid bat - Ia io,
although there is a thrip with a single-letter species name - Plesiothrips o
!
More strangely named
butterflies
here.
Former common
names of British butterflies
here.
More fascinating scientific
names -
Earthlink Taxonomic Puns
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