moth larvaCecropia caterpillar

August 18, 2020

Some of the most widespread and recognizable insects in the world have a strange family name--Lepidoptera--and were given this several hundred years ago from the ancient Greek words “scale” +“wing”.  We know them as butterflies and moths, and some 180,000 species have been named. 

These insects are characterized by several unique features. The most apparent is the presence of scales that cover their bodies and wings (and give them their Greek name), and a tubular mouthpart used for feeding and sucking. They also all undergo a four-stage life cycle; egg, larva, pupa, and adult.

The larva, usually called a caterpillar, is completely different from the adult and has a cylindrical body with a well-developed head, mandible mouth parts, three pairs of legs in the front of its body and from none up to five pairs of prolegs on the rear. As they grow, these larvae go through a series of stages and eventually enter into a resting state called a pupa while they change into their adult form. 

Butterflies and moths play an important role in the natural ecosystem as pollinators and as food in the food chain; on the other hand, their larvae are considered very troublesome to vegetation in agriculture, as their main source of food is often live plant matter and they are very prolific.  In many species, the female may produce from 200 to 600 eggs, while in others, the number may approach 30,000 eggs in just one day. The caterpillars hatching from these eggs can cause enormous damage to large quantities of crops.

There are also approximately 3,500 species of insects that occur worldwide and are named “skippers”for their fast, darting flight.   Many people consider these an intermediate form between butterflies and moths but technically they are also butterflies.   At last estimate, there were roughly 174,250 lepidopteran species described, with butterflies and skippers estimated to comprise around 17,950, and moths making up the rest.   The vast majority of Lepidoptera are to be found in the tropics, but substantial diversity exists on most continents.

North America has over 700 species of butterflies and over 11,000 species of moths.  Moths evolved long before butterflies, with fossils having been found that may be 190 million years old. Both types of Lepidoptera are thought to have evolved along with flowering plants, mainly because most modern species feed on flowering plants, both as adults and larvae. 

Like all insects, the moth, butterfly and skipper have exoskeletons and jointed limbs, but unlike other insects, the three all have membranous wings covered with pigmented scales.   The moth usually has plain colors and patterns and is nocturnal, while butterflies are often adorned in flashy patterns and colors and are abroad in the daylight.  One better guiding characteristic is that butterflies have thin antennae with small clubs at the end while moth antennae are usually very feathery with no club.   The skipper, with characteristics of both the moth and the butterfly, falls into an intermediate stage with its antennae clubs bent backward like a crochet hook.

Butterflies have the typical four-stage insect life cycle. Winged females lay eggs on the food plants on which their larvae will feed. The caterpillars grow, sometimes very rapidly, and when fully developed, the skin splits, revealing a dormant form covered with a hard shell and called a chrysalis.  When inner development is complete, this splits and the adult insect climbs out, and after its wings have expanded and dried, it flies off. Some butterflies, especially in the tropics, have several generations in a year, while others have a single generation, and a few in cold locations may take several years to pass through their entire life cycle.

Many moth larvae are equipped with spinnerets, silk-spinning organs that are complex structures with many microscopic spigots, each producing one filament.  These moth larvae use the silk to make protective cocoons to house their pupae and when they emerge, they are fully grown moths with wings.  Evidence has been discovered that this silk was first used in China some 4500 years ago, and recently, the silk industry in the United States has produced some 300,000,000 pounds of raw silk, worth about $250,000,000 each year.

On the other hand, the caterpillars of the gypsy moth cause severe damage to forests in the northeastern United States, and major agriculture pests round the world include cabbage moths, corn borers, bollworms, codling moths.  Other moths are commonly decried because their larvae eat fabric fibers such as wool in clothing, rugs, and heavy blankets. Despite being notorious for eating wool, most large adult moths do not eat at all as they have no mouth parts, while most smaller ones drink nectar like the butterflies. 

This is prime time of the year for the adult Lepidopteras and any flower garden is sure to harbor several such visitors.  Sit nearby and count how many species of these interesting creatures you can catalog and perhaps photograph the more spectacular ones.  They have often been referred to as flying flowers.