Wednesday, April 4, 2018

ENTOMOLOGY: Lepidopterans - Moths, Butterflies and Skippers: A Study of Biodiversity

Dr Abe V Rotor

Moth of cutworm (Prodinia litura) may be mistaken as skipper. 

Since I was I child I have been fascinated by the Lepidopterans. The butterflies are the most beautiful of all insects; one moth is considered the biggest insect in the world (Atlas atlas or mariposa has a wing expanse of nearly a foot); and the skipper gives goosebumps because they are believed by old folks as representatives of the world of spirits as night approaches. (Skippers are actually crepuscular, that is, they are active at dusk). Parents used to warn us kids to be home before dark.

One thing about lepidopterans, that many of us are not aware of, is that they all come from caterpillars, the name of their larvae, the counterpart of maggots in flies (Diptera), and grubs in beetles (Coleoptera). Caterpillars are also referred to as worms by farmers. Many are destructive, among them are armyworms and cutworms, corn borers, earworms, tobacco hornworm, rice stemborer, and the spiny tussock caterpillar (higad).

Yet it would be grossly unjust that Lepidopterans escaped from Pandora's Box. Without them there would be less fruits and vegetables. Forests and grasslands would not be as rich in stand as they are. It is because lepidopterans are the most efficient pollinators, equaled only by Hymenopterans (bees, wasps, and ants). They thin out unwanted plants, keeping those resistant ones to carry on their genes to the next generation. They convert organic compounds into their elemental components, the caterpillar acting as a living digester. They are nature's fertilizer manufacturers.

As pollinators the three lepidopterans have divided work hours: butterflies during the day, moths at night, and skippers at dusk and dawn. While they are selective in their nectar food, they have alternative hosts which enable them to tie up with all seasons, and to expand their geographic range of feeding. Curious as a child, I would uncoil their siphon, the counterpart of the tongue of most animals. The siphon works like a softdrinks straw, except that it is retractable and can be readily tucked neatly underneath like garden hose.

Why are lepidopterans so varied? How did the different species evolve? Speciation is a term in evolution - the formation of a new species. But when is a species a new species, and different from its parent stock?

It baffles the mind to know there are millions of species of plants and animals. If the lower forms of life are included, and those living in the forbidding depth of the sea, and those in the past which are known only by their fossils, indeed the biosphere, the living world in which we live in today, is the biggest mystery on earth.

Species evolve into new species, ad infinitum. This is the foundation of diversity. The more diverse the living world is, the more the members can adapt to the changing environment, both in short term and long - and continuing, covering thousands or millions of years. Evolution in general tends to progress towards not only the preservation of a species but also the enhancement of the survival of others, directly and indirectly. And most important, it prepares the formation of new species, which explains the increasing diversity of life forms.

This means that the lepidopterans continue to evolve, so that more and more species and subspecies are likely to be formed. Because this takes a very long time, there is no direct reference to prove that the skipper may have developed from moth and butterfly. Or the moth evolved from skipper and butterfly. But because of certain commonalities in their morphology and physiology they are grouped under one family.

Thus we have the so-called grouping of organisms into different levels beginning at the top as Phylum (animals) or Division (plants). Similarities of members become more pronounced on the level of Order, and much more in the Family. The closest similarities are found on the Genus level. In fact the members may be difficult to differentiate, so that we can only surmise speciation is still going on.

Life on earth is still expanding. It is actually explosion of life forms and number in slow motion. Like  the universe expanding in space since the Big Bang, so with life forms expanding in the biosphere. This is the way the Great Maker has intended it to be - through the natural laws that govern dynamic balance and stability called homeostasis.

The lepidopterans provide the ideal specimen to ponder on this great phenomenon. ~

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