Aberrations
-An aberration is a variation in the wing pattern or colouring of a butterfly species which does not conform with the normal appearance of the species. This can transpire as a genetic or environmental variation, differing from the standard form of the species. Aberrations are normally very rare, some aberrant forms however can turn up on a recurrent basis and consequently, many have been given distinctive names.
Aberrations happen for an array of reasons; commonly they are caused due to extreme temperature changes, particularly during the time a butterfly is developing within the chrysalis or pupal stage. An exceptionally cold environment can result in unusually dark forms of some species, whilst abrupt temperature changes or extreme temperature (heat shock) may well result in striking differences in wing pattern.
Variation(Forms)
-Variation or 'forms' are found frequently within a species and the appearance of the butterfly differs slightly, depending on its geographical distribution and subsequent climate that they are subjected too, over time due to species interaction and inbreeding this can lead to new 'sub-species'.
A term often used is 'Cline' which means 'a gradation in one or more characteristics within a species or other taxon, especially between different populations'. They display continuing phenotypic and/or genetic differences over a geographical region, normally as a product of environmental heterogeneity. Genetically, clines occur from the change of allele frequencies within the gene pool of a particular species.
Natural barriers, such as mountains or large bodies of water but also man-made barriers such as towns and cities; expanding with the increase in human development, can prevent some, weak flying species from interacting with one anothers colony. This lack of 'new blood' can result with interbreeding of a colony so that its specific adaptations and subsequent appearance become more pronounced with each generation; having a negative effect on a weakened gene pool and eventually local extinctions. Other colonies that are able to exchange genes do not have this issue, for they are able to maintain a healthy population with the specific adaptions still in tact.
Sexual Dimorphism
-The different sexes in one, same species can vary noticeably in wing coloration or even shape; but this is a more subtle difference. This contrast between the two genders is known as being ‘sexually dimorphic’. In numerous species, sexual dimorphism does not happen and in others it is tremendously understated whereas in some, the difference is constant and obvious with wing colour and pattern being very unlike the other sex in the identical species.
-Androconica (Sex Brands)
--Some species of butterfly appear to have very little difference at first between the two sexes, except in a number of Male butterflies where the only small difference in wing pattern is the sex brand, also known as the androconica. These areas on both forewings of a male butterfly, distinguish it from the comparatively similar female. The androconica is basically a region of specialised wing scales that is designed to release sexual pheromones to attract a female of the same species.
Where the androconica of the male is not clearly observable there are alternative variations that can provide the answer; some include wing shape and body width or length.
Age
An obvious change in appearance which I feel should be described here is age and the effect it has on butterflies delicate wings.
A butterfly starts its life, provided a perfect emergence has taken place, as a pristine insect with beautiful, delicate and lightweight wings, ideal for a life of flight. Covered in dust-like scales, in some species these are lost almost immediately within the first few flights; an example is the Black-veined white (extinct in UK). Others lose their scales slightly more gradually, like the Marsh Fritillary that was once known by another name 'Greasy Fritillary' by the visual effect the loss of surface scales and subsequent colour has.
Fresh specimens tend to have gorgeous, bright colours (depending on species) and complete wings but as the ravages of weather, predators and other environmental factors take hold, the appearance can differ completely, some becoming almost unrecognisable.
'Fading' of a butterflies scales due to old age can sometimes be mistaken as a genetic 'aberration' with lighter colour than usual but this is a misconseption.
