Butterflies and moths are most numerous in the tropics, but many temperate areas have a bountiful supply of many species. They are insects and therefore have three main body regions. Those parts being the head , the thorax, and the abdomen. They also have three pairs of jointed legs, and one pair of antennae.
The word Lepidoptera is derived from two Greek words. First is lepidos, meaning scales. Second is ptera, meaning wings. What distinguishes lepidopteras from all other insects is their scaled wings. The scales rub off as colored powder when the butterflies and moths are handled.
Next to Coleoptera, Lepidoptera is the largest order of insects. Lepidoptera have about 120,000 species. About 10,000 of these are in North America. There are three suborders of Lepidoptera. Jugatae has about 250 primitive species that somewhat resemble caddis-flies. The second suborder is Frenatae. Most moths fall into the Frenatae category. The third is Rhopalocera. That is what butterflies and skippers are.
The smallest type of Lepidoptera are nepticulid moths. They measure only 0.1 inch.
The Suborder Rhopalocera is divided into two super-families. These are Papiplionoidea and Hesperioidea. Papilionoidea includes nineteen families of butterflies. Hesperioidea is two families of skippers. It’s easy to identify butterflies and skippers because of the shape and position of their antennae.
The suborder Frenatae had about fifty families of North American Moths. The presence and position of simple eyes and leg spines, the nature of the antennae, and the shape and venation of the wings are used to identify moths.
Lepidoptera develop by a complete metamorphosis which is characterized by four distict stages. First, the egg hatches into a larva. The larva is the caterpillar of butterflies and moths. It feeds, grows, and molts several times before it eventually makes a transformation into a pupa. The pupa is what is commonly referred to as cocoon. After a period of time a winged adult emerges.
The eggs can very greatly in size and shape. Many are smooth and spherical; others are flattened, conical, barrel- or spindle-shaped. Most have ornaments of ribs, pits, or grooves, or with networks of fine ridges. Each egg has a small hole in which it is fertilized through. Some species lay eggs singly, others in small clusters, or some in one egg mass. Sometimes eggs are dropped at random, depending on the species, but are usually deposited in some definite pattern such as rows on the plant that will serve as the larva’s food. Eggs that are laid in the summer time usually are thin-coated while those that over winter before hatching have a thicker outer coat and are sometimes covered with a hair like material from the moth. Some are covered by a foamy layer. Most eggs hatch within a few days, when the larva eats its way out.
Most larvae are ravenous feeders. Some mature in as little as a week while others take several months. Most actively feed until they go into the pupal stage. Some become dormant during the dry summer months. Others hibernate. All larvae of Lepidoptera are caterpillars but some are known as slugs, worms, or borers. They feed on fruits of plants, flowers, and leaves, and occasionally by boring into stems and wood. There are some species of Lepidoptera which are scavengers as larvae. Some feed on insects such as plant lice and scale insects. There are even a few who feed on animal products like wool, silk, or feathers.
Some caterpillars are green, with skin so thin and transparent that the color of the chloroplasts in the plant food show through. Many are brightly marked and have bold patterns. Some have hairs, spines, horns, bumps, and knobs. Hairiness ranges from a trace of hair to a complete furry covering, but most species are smooth skinned. Some species have hairs and spines which are poisonous and irritating to the human skin.
As a caterpillar grows, it molts. This allows a new period of growth. In the periods between molts the larvae are called instar. Early instars may differ from older larvae in in their shape, color, and markings. Like the adult, caterpillars have three body regions. Those are the head, thorax, and abdomen. The head has five or six fused segments and a pair of short antennae. On each side of the head are pairs of ocelli, which are very simple eyes, that are usually in a semicircle. The mouthparts include a strong pair of mandibles, a labrum, a labium, and two palpi, which are segmented sensory structures. Often the labium has a spinneret that is used for making silk filaments. The thorax has three segments, and on each is a pair of short, jointed legs that end in claws. On each side of the first thoracic segment is a spiracle opening for breathing, which is the only pair on the thorax. The abdomen usually has ten segments and bears two to five pairs of short and fleshy prolegs, usually on the third, fourth, fifth, sixth, and tenth segments. The last segment has the last and largest pair, the anal prolegs. On the first eight abdominal segments spiracles can occur on each side. Many species have the area around these colored.
The third stage is the resting form which is the Pupae stage. It is during this stage that the Lepidoptera transforms into an adult. Most spend the winter as pupae in temperate regions, but for some species this stage lasts only a few days. What happens during this stage is extremely complex. Prolegs are lost in a pre-pupal stage. Later the mouthparts transform from chewing mandibles to a long proboscis (though some adults do not have this). Wings and reproductive organs develop. The actual change is caused by hormones but external factors such as moisture and temperature may trigger these changes. The pupa may rest for some time before the actual transformation into the adult occurs.
Before changing into the naked pupa, the butterfly larva attaches itself to a firm support. This is known as a chrysalis. Larvae of some moths burrow into the ground and pupate. Some pupate amid dead leaves, grass, or in debris on the ground. Many moth larvae spin some kind of a cocoon that surrounds the pupa. Moths usually take much longer than butterflies to emerge from the pupa. Both emerge with soft, limp, moist wings which slowly expand as fluids are pumped through their veins. These veins later harden to provide rigid support for the wing membrane.
Adult butterflies and moths have a pair of segmented antennae and a pair of large, rounded, compound eyes on their head. Moths often also have a pair of simple eyes. All butterflies and most moths have a coiled proboscis, which unrolls into a long sucking tube through which the adult feeds on nectar and other fluids. Sometimes this tube is as long as the adult’s body. On each of the three segments of the thorax are a pair of five-jointed legs. On some butterflies the first pair of legs is reduced and females of some moths do not even have these first pair of legs. Attached to the second and third segments of the thorax most butterflies and moths have two pairs of membranous wings. There are a few kinds of wingless Lepidoptera, however. The vein pattern of these wings is important in identification. At the end of the ten-segmented abdomen are the sex organs. These are used in the accurate identification of most species. Females usually have larger abdomens than the males. Males can be identified by the claspers of the sex organs which protrude as plate-like structures at the end of the last segment.
Butterflies and Moths: A Guide to the more common American Species by Robert T. Mitchell and Herbert S. Zim