Greetings once again bug fans! It’s time for another edition of Friday Flyers! Every Friday our goal is to bring you an interesting topic, and we want to introduce you to a wide variety of “Flyers”. We’ve shown you spectacular beauty, profound ugliness, and something from every region of the world. This week we’d like to bring you a little more “collector” oriented topic. Today we’re going to talk about variation. What we mean is; variation of color and pattern within a species, and how and why it occurs. Don’t panic, we won’t get very technical.
A good place to start is with the wing itself. A butterfly wing is a transparent membrane stretched between semi-rigid veins, covered with colored scales. The scales are attached to the surface of the wing membrane and overlap like roof shingles. They are individually colored by pigment chemicals into all the colors we see. The arrangement of colors and patterns is genetically programmed, just like your eye color or hair color. In most butterfly species, the patterns and colors are very consistent from individual to individual, and they have to be. A species has to rely on consistency in wing patterns to ensure proper mate selection, protection from predators, and camouflage while at rest.
There are exceptions to this rule. Some butterflies vary so much that the various forms have frequently been misidentified as different species. Genetics has helped tremendously in sorting out these faulty identifications. Today we know that the genetic blueprint for wing patterns is controlled by only a few genes. These genes determine what color pigments are formed. The “pigment formation” genes will normally produce only their preprogrammed colors, but they can be influenced by other factors such as chemical imbalances, temperature, humidity, etc. When these outside factors occur, the wing scales are pigmented to a color other than the originally intended color. If the color or pattern change occurs in an individual butterfly, that specimen is called an “Aberrant” specimen. When the same type of pigment change occurs repeatedly in a butterfly species, the resulting new pattern is called a “Form”, and when the “Form” becomes the dominant pattern in a particular location, the form will be designated as a “Subspecies”.
Many butterfly species have multiple forms. We have photographed several different types of forms to help illustrate this phenomenon. First is a great example of forms that are caused by geographic isolation. Our photo shows a museum drawer of variations in the South Pacific Swallowtail species Papilio aegeus. These are all females, each from a different mainland location or a different island. Geographic isolation has allowed them to evolve independently, and so each form is now the only form in its location. A drawer like this Papilio aegeus drawer probably took many years to assemble, and is of great value to the scientific community. It represents a permanent record of species variability in an ever changing world.
Second is an example of multiple forms coexisting as equals. These three Oxytenis moths all have the same pattern, but in three different colors. All were collected at the same location in Ecuador on the same day. Relatively few species have multiple forms coexisting, but these moths don’t seem to be a bit confused. Perhaps it is because they are night flyers, and therefore color plays a less important visual role in mate selection.
Our third example is a composite photo of the undersides of two South American Nymphalid butterfly species. This photo shows an example of Wet Season / Dry Season forms. The Dry Season forms are more drab. This aids these butterflies in camouflaging themselves among the dry dead leaves. Notice that the basic pattern markings are still visible, just subdued. The differences in seasonal rainfall experienced by the butterfly chrysalis cause the developing butterfly to synthesize different pigments for the appropriate seasonal camouflage requirements.
So now that we’ve explained a little about how and why variation occurs, here’s what’s important about it. Butterflies are perhaps the best scientific experimental subjects to explore and test theories on species origin, biochemistry, genetics, and a wide variety of environmental issues. They reproduce in enormous numbers, mature in a month or two, and show easily visible wing pattern changes. They are perfect scientific models!
If you are a collector who is ready to take the next step in making your collection more comprehensive, we can hel!. Our Wonders Of Nature department will be happy to assemble custom species assortments and frame them for you. Collecting variations is an interesting and scientifically important way to collect insects, and we can get you started with some suggestions of some very beautiful species to add to your collection.
We hope you enjoyed this week’s edition of Friday Flyers. We love sharing our interest in butterflies and insects with you. Please enjoy the photos we have posted with this week’s edition, and be sure to see all the previous pictures in our Friday Flyers album. Remember to “like” our Wonders Of Nature page, and be sure to pass it along to all your Facebook Friends. We hope you’ll visit our Wonders Of Nature department soon, and we look forward to seeing you.