2006-02-03 / Columnists

Drawing On Science

by Stephen Yaeger

Butterflies And Moths

This month’s topic was suggested by Colin, one of my nephew’s classmates. He asked if I could write about butterflies. I thought I’d go one better and write about moths too.

Butterflies and moths belong to a large group of insects called Lepidoptera ; can you say leh-peh-DOP-tuh-ra? ( lepido= scale ; tera= wings). Lepidoptera, then, means scaly wings. These insects normally have four large wings. Each wing is covered with loose, slippery scales. If a predator gets hold of a wing, the scales come loose and the butterfly or moth escapes. Some female moths have short wings and others are wingless. There are some basic ways you can distinguish between butterflies and moths. You can easily tell the difference between these two guys by examining the antennae (those two do-hickys sticking out of the top of their heads). Butterflies have club-tipped antennae. Moths have antennae that may have feathery, threadlike, hairy or filamentous tips. Butterfly bodies are slender, while moths have thick bodies. When not flying butterflies keep their wings up and together, but moths keep their wings extended outward to the side. Moths are generally nocturnal (=active at night) or crepuscular (=active at dawn), while butterflies are mostly diurnal (=active during the day).

Butterflies and moths have a long sucking tube called a proboscis (pro-BO-sis), with which they suck up the nectar of flowers. As such, they are very good at pollenizing flowers. They will also feed on sugary stuff made by other insects, tree stumps, and decaying fruit. Some will even feed on poop (yeah, I know, but they love it!). Sometimes you can see butterflies drinking water from puddles. When not feeding, their sucking tubes are coiled up like a spring.

Females usually lay eggs in large masses on food plants. Some may spread out their eggs on or near the plant. The eggs hatch in a few days or weeks or don’t hatch until the following year. Caterpillars (=larvae) hatch and begin to feed immediately. Nearly all caterpillars eat plants. Some are restricted to a particular plant or group of plants. Some caterpillars are predators. They feed on leafhoppers, mealybugs and other insects. They have from two to five pairs of very small legs with hooks. The hooks allow them to cling to branches and things. Some caterpillars are naked; some are covered with setae (= hair). Caterpillars may remain on the food plant or nearby until ready to change into the adult insect.

A special liquid is made inside the insect and then passed out of the mouth. It hardens into silk. The silken threads are used by the caterpillar to stick to surfaces or to form a cocoon or to make a shelter. Many moth larvae spin cocoons around themselves. Inside the cocoon, a moth will change into a pupa. Many butterfly larvae do not spin cocoons. Instead they hang upside down from a silk thread and begin changing into a pupa ( chrysalis ). Once the pupal stage passes, the adult moth/ butterfly emerges. The new adult pumps blood into its wrinkled, folded wings. The wings expand and spread out. When they dry the insect is ready to fly away.

There are many color patterns among butterflies and moths. Some patterns help to conceal the insect while others warn potential predators that the butterfly or moth may be distasteful. Some species have large circles on the wings. These are known as eyespots . When the insect is threatened, it will suddenly spread out its wings exposing the eyespots. The predator is startled, giving its potential meal a chance to escape.

Now here are some facts you can talk about at dinnertime to show how smart you are. The largest butterfly is the Queen Alexandra’s Birdwing. An entomologist (one who studies insects) knows this one by its scientific name: Omithoptera alexandrae. It calls Papua New Guinea its home. It has a wingspan of 280 mm (about 11 inches) and is an endangered species. The smallest butterfly is the Western Pygmy Blue, Brephidium exilis , found in the southern United States. It has a wingspan of only 15 to 19 mm (about 0.5 to 0.7 inches). The smallest moths are known as leafminers. They have a wingspan of 2.5 mm or 0.1 inch.

Questions/comments/suggestions? E-mail Steve: Drawingonscience@ aol.com

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