What is an aberration?
Well, an aberration is when the wing pattern of a butterfly species is different to the normal pattern. This can occur as a genetic or environmentally produced variation on the usual form of the
species. Aberrations are generally very rare. Some aberrant forms are recurrent with many being specifically named such as the aberrant Comma form reichstettensis shown below photographed at Fermyn Wood (Northamptonshire) in 2006.
How do aberrations occur?
Butterfly aberrations occur for a variety of reasons, generally, extreme temperature changes especially while the butterfly is developing during the pupal (chrysalis) stage. Very cold conditions can produce very dark forms of some
species while heat shock may cause dramatic changes in wing pattern.
What are variations?
These are more common occurrences within a species and in general a reasonably consistent variations. Variations may occur due to local geography, climate and population interaction. Small local populations (colonies) which do not or cannot breed with other colonies due to obstruction (by mountain ranges or sea) may result in interbreeding within the colony. In Britain, many species are at risk due to habitat fragmentation and isolation of colonies due to road building, housing and industrial developments. On their own, these developments rarely pose any major threat except for species which are present in very localised colonies... however, the combination of multiple developments over time can cause regional extinctions.
Variation may also occur over a butterflies individual life span. Young, freshly emerged butterflies tend to have a rich coloration and undamaged wings while old specimens may have damaged wings and coloration which has faded. This is generally due to the loss of surface scales on the wings.
A good example of general butterfly variation is the Small Copper Lycaena phlaeas which also has a common variation known as Lycaena phlaeas form caeruleopunctata (see below).
What's Sexual Dimorphism?
Males and females of the same species may differ dramatically in coloration from each other. Such species are said to be sexually dimorphic. In many species, sexual dimorphism is not present while in others, it may only be a subtle but consistent difference in wing coloration and pattern. The Common Blue is a species which displays a classic example of sexual dimorphism, where the male is completely blue while the female is brown sometimes with hints of blue towards the base of the wings nearest the body (see below).
Males of the species may only vary in wing pattern in the area known as the androconica or sex brand. Pheromones are released from these patches in order to attract a female.
Aberration Far Left: Comma aberrant form reichstettensis Left: Normal Comma
Common Variations Far Left: Brown Argus (Grafton Wood, Worcestershire) Left: Brown Argus (Isle of Wight)
Note how large the orange bands (formed from joining Lunule's on the edges on the wings far left, reduced to spots on the more common version of the Brown Argus on the right.
Wear and Tear Far Left: A rather tatty Comma showing the effects of both age and missing wing parts, probably the result of a bird strike... this individual making a lucky escape.
Left: A male Silver-washed Fritillary showing the effects of age.
