Butterfly

Butterfly:

They can see polarized light and therefore orient even in cloudy conditions. These migrations take place over a number of generations and no single individual completes the whole trip. The long proboscis can be coiled when not in use for sipping nectar from flowers.

Nearly all butterflies are diurnal, have relatively bright colors, and hold their wings vertically above their bodies when at rest, unlike the majority of moths which fly by night, are often cryptically colored (well camouflaged), and either hold their wings flat (touching the surface on which the moth is standing) or fold them closely over their bodies. Simple photoreceptor cells located at the genitals are important for this and other adult behaviors. The male passes a spermatophore to the female; to reduce sperm competition, he may cover her with his scent, or in some species such as the Apollos (Parnassias) plugs her genital opening to prevent her from mating again.

The vast majority of butterflies have a four-stage life cycle; egg, larva (caterpillar), pupa (chrysalis) and imago (adult). further information: Glossary of entomology terms and Comparison of butterflies and moths

Unlike butterflies, most moths (like Laothoe populi) fly by night and hide by day.

Butterfly adults are characterized by their four scale-covered wings, which give the Lepidoptera their name. The polarized light near the ultraviolet spectrum appears to be particularly important. Many migratory butterflies live in semi-arid areas where breeding seasons are short. The life histories of their host plants also influence butterfly behavior.

Life cycle

Life cycle of the monarch butterfly

Mating pair of spotted fritillaries on greater pignut

Butterflies in their adult stage can live from a week to nearly a year depending on the species. Most butterflies have the ZW sex-determination system where females are the heterogametic sex (ZW) and males homogametic.

Distribution and migration

See also: Lists of butterflies of Australia (Tasmania, Victoria), Britain, India, Menorca, North America, Taiwan, and Trinidad and Tobago

Further information: Lepidoptera migration, Insect migration, and Animal navigation

Butterflies are distributed worldwide except Antarctica, totaling some 18,500 species. Of these, 775 are Nearctic; 7,700 Neotropical; 1,575 Palearctic; 3,650 Afrotropical; and 4,800 are distributed across the combined Oriental and Australian/Oceania regions. The monarch butterfly is native to the Americas, but in the nineteenth century or before, spread across the world, and is now found in Australia, New Zealand, other parts of Oceania, and the Iberian Peninsula. The eastern North American population of monarchs can travel thousands of miles south-west to overwintering sites in Mexico. There is a reverse migration in the spring. It has recently been shown that the British painted lady undertakes a 9,000-mile round trip in a series of steps by up to six successive generations, from tropical Africa to the Arctic Circle — almost double the length of the famous migrations undertaken by monarch.  Spectacular large-scale migrations associated with the monsoon are seen in peninsular India. Migrations have been studied in more recent times using wing tags and also using stable hydrogen isotopes.

Butterflies navigate using a time-compensated sun compass. The pupa or chrysalis, unlike that of moths, is not wrapped in a cocoon.

Many butterflies are sexually dimorphic. These scales give butterfly wings their color: they are pigmented with melanin's that give them blacks and browns, as well as uric acid derivatives and flavones that give them yellows, but many of the blues, greens, reds and iridescent colors are created by structural coloration produced by the micro-structures of the scales and hairs.

As in all insects, the body is divided into three sections: the head, thorax, and abdomen. The thorax is composed of three segments, each with a pair of legs. Butterflies then land on the ground or on a perch to mate. Copulation takes place tail-to-tail and may last from minutes to hours. It is not clear how it dispersed; adults may have been blown by the wind or larvae or pupae may have been accidentally transported by humans, but the presence of suitable host plants in their new environment was a necessity for their successful establishment.

Monarch migration route

Overwintering monarchs cluster on oyamel trees near Angangueo, Mexico.

Many butterflies, such as the painted lady, monarch, and several danaine migrate for long distances. In most families of butterfly, the antennae are clubbed, unlike those of moths which may be threadlike or feathery. Many species have long larval life stages while others can remain dormant in their pupal or egg stages and thereby survive winters. The Melissa Arctic (Oineils melissa) overwinters twice as a caterpillar. Butterflies may have one or more broods per year. The number of generations per year varies from temperate to tropical regions with tropical regions showing a trend towards multivoltine.

The male small skipper (Themelis's sylvestris) has pheromone-releasing "sex brands" (dark line) on the upper side of its forewings.

Courtship is often aerial and often involves pheromones. They have cylindrical bodies, with ten segments to the abdomen, generally with short prolegs on segments 3–6 and 10; the three pairs of true legs on the thorax have five segments each. Many are well camouflaged; others are aposematic with bright colors and bristly projections containing toxic chemicals obtained from their food plants. In the genera Colias, Erebia, Echoe, and Parnassias, a small number of species are known that reproduce semi-parthenogenetically; when the female dies, a partially developed larva emerges from her abdomen. Some day-flying moths, such as the hummingbird hawkmoth, are exceptions to these rules.

Butterfly larvae, caterpillars, have a hard (sclerotized) head with strong mandibles used for cutting their food, most often leaves.