Natural History Photographs


Some thoughts about variation
in the colours of Butterflies


Butterflies differ in color. This is trivially true if one compares different species, but it is non-trivially true within a species. Within an individual's life span, within a population, between spring and summer generation, between different geographic areas: variation in coloration is rife. In this page I give examples of the multifarious ways in which variation in coloration can be observed.

The various forms of color variation can be conceptualized as arising from two sources: space and time. Two butterflies can be near or far in space and time. Defining the differences in space and time means defining the sources of variation. I'll show some examples from various combinations of near by and far away in space as well as in time.

Variation within an individual's lifetime
If distance is zero, while time varies only slightly one deals with variation in the lifetime of a single individual. Don't underestimate this source: it can cause dramatic variation indeed. Here are some examples.

The Painted Lady, Vanessa cardui

Top row: When fresh, that is, when just eclosed from the pupa, the Painted Lady has a salmon glow about it, especially the underside of the forewings.
Bottom row: The pigments causing this pink shade tend to become dull with long exposure to air. The specimen left already lacks the fine colors of fresh specimens; the right specimen has lost not only color, but also lots of wing...


Zerynthia rumina. Left is a nice fresh specimen, but the one on the right is an old lady or gent. Its wings have become translucent, because most yellow scales are lost.




Vanessa atalanta. This is clearly a fresh specimen - though the right wings shows obvious signs of damage. I suspect this butterfly got stuck with the right wings and could only liberate itself by pulling them out - at considerable damage to the color pattern.




Variation between individuals within populations
If both spatial and temporal distance are nonzero but small, the situation indicated is the population within one generation. The additional source of variation is between individuals when they eclose. In some species this source is rather small. For instance, Red Admirals (Vanessa atalanta) may differ in size, but their color pattern is remarkably stable.



The most obvious interindividual variation is in the color of the red band, but most of this variation is due to the previous source - that is, to wear and tear.

But the Red Admiral is rather uncharacteristic as regards variation. In many species, there is a at least one major source of variation: sex.



Males and Females
Males and females may differ in coloration very much indeed. If they do, a species is said to be sexually dimorphic. Sexual dimorphy can be totally absent, as in the genera Nymphalis and Vanessa. It may be present but not pronounced, as in in many species. But it can be very pronounced indeed, as in many blues. Here are some examples of more pronounced sexual dimorphy.


Male Female
Black-veined white, Aporia crataegi.

Lycaena virgaurea montana

Common Blue, Polyommatus icarus

Common Blue, Polyommatus icarus



Within population phenotypic variation
In general, most individuals within a population differ in there genetic make-up, as well as in the environmental conditions they were exposed to during development. As a result, they do not all look the same. The technical term for this is phenotipc variation. There is hardly a limit to this, but extreme aberrations are rare. Aberrations tend to be discontinous forms of variation. The more common variation tends to be gradual. Here is an example.
Summer generation of the Green-veined White, Pieris napi.

Both whites are from the summer generation. The form on the left panel is so different that is got its own name: forma napaea. It's so unlike 'typical' napi that you may even mistake it for rapae.
These two specimens show various kinds of variation. First, the right specimen has blue scales above the orange band of the hind-wing - a feature that may even be much more strongly developed. Second, the spots on the fore-wing differ substantially in size. And third, the red band in the hind wing differs in shape.


Aberrations
As stated above, aberrations tend to be discontinous forms of variation. There is no clear cut difference between a variation and an aberration. The Small Copper shown above, with blue spots, is described as an aberration, but I found it to be a very common variation. It may be present to some degree in over half of the butterflies in a population. That sounds not very aberrant, and therfore I prefer the term forma instead of aberration.

But there are many variations that may really count as aberrations, because (i) they differ substantially specimens in a population, and (ii) there are no intermediates between the normal type and the aberration, and (iii) they are very rare. For example, I've seen thousands of Red Admirals, but there were only two aberrations among these.

Although any particular aberration is generally very rare indeed, there are so many of them that one certainly has the possibility to observe some aberration every now and then. Here are a few I knew to photograph.

Brimstone, Gonepteryx rhamni
Normal form on the left, unnamed aberration on the right.
A Fritillary, Melitaea spec.
Unnamed aberration.
The Small Copper, Lycaena phlaeas
Typical (top row) and var. alba (bottom rwo).
The Speckled Wood, Pararge aegeria
Typical (left) and aberrant form (right).
Variation between generations within populations
Some butterfly species fly in only one generation per year. But many others, especially the smaller ones, fly at different times of the year, for instance in spring and during the summer. This means that the larvae and pupae develop under different conditions. Especially the weather will make a difference, but there are also other differences. Day length varies very predictable, and may act as a cue to base developmental decisions on. Food quality may also be different. Since environmental conditions might affect development, butterflies of different generations might show different colors. The technical term for different colors in different generations is seasonal dimorphy.
The Wood White, Leptidea sinapis
Spring generation on the left, summer generation on the right. The absence of dark markings in the summer specimen may be quite extreme. Both pictures taken in the same area, see habitat.


The Comma, Polygonia c-album
The voltinism (i.e., number of generations) of the Comma is slightly complex. They hibernate as adults, and it is always the dark form shown left that hibernates. The hibernater's offspring may develop into adult butterflies that reproduce in the same year; these adults are or the lightly colored form on the right. Alternatively, they may develop into adults that hibernate before reproducing. Such butterflies are of the dark form. The offspring of the light form produces dark butterflies that always hibernate.

On top of this intergenerational variation comes sexual dimorphism. The two photographs below show a female (left) and a male (right) of the overwintering generation.


The Map butterfly, Araschnia levana
Spring generation on the left, summer generation on the right. The most extreme case of seasonal dimorphy in European butterflies. Linnaeus even ranked the two forms as different species!
Geographic variation
Quite often butterflies in different geographic areas are different from each other. Although two individuals from different populations may occasionaly still show a strong semblance, the populations as a whole can still be different. If this is the case, the populations show signs of geographic variation.

Geographic variation is due to variation in space rather than in time. However, it is invariably confounded with other sources of variation. One always has to account for intra-individual variation (the first source mentioned on this page). Moreover, different geographic regions vary in climate, affecting the timing of generations. Other environmental qualities most likey also differ. As a result, the populations may have genetically adapted to their local environment. If so, the genetic difference is an important cause of variation. Here is a typical example of the confounded nature of geographical variation:

The Scarce Swallowtail, Iphiclides podalirius
Ronda, Spain; April 1982. Jaca, Spain; May 1982.
Montagne du Luberon, France; June 1990.
There's much intra-individual variation here. One butterfly has lost one tail, one has lost half of both its tails. The Jaca specimen is fresh, the Ronda specimen already worn, the Luberon specimen is heavily worn indeed. They are all from the first generation, flying at different times due to climatic differences. On top of this there is geographic variation. The Iberian butterflies have a more whitish ground color, those north of the Pyrenean Mountains a more yellowish one. This is hard to see in these photographs due to differences in wear in tear. Another difference is that the Iberian specimens have broader black stripes, as can be observed here too.