Migration

Many butterflies migrate over long distances. Particularly famous migrations are those of the Monarch butterfly from Mexico to northern USA and southern Canada, a distance of about 4000 to 4800 km (25003000 miles). Other well known migratory species include the Painted Lady and several of the Danaine butterflies. Spectacular and large scale migrations associated with the Monsoons are seen in peninsular India.[36] Migrations have been studied in more recent times using wing tags and also using stable hydrogen isotopes.[37][38] Butterflies have been shown to navigate using time compensated sun compasses. They can see polarized light and therefore orient even in cloudy conditions. The polarized light in the region close to the ultraviolet spectrum is suggested to be particularly important.[39] It is suggested that most migratory butterflies are those that belong to semi-arid areas where breeding seasons are short.[40] The life-histories of their host plants also influence the strategies of the butterflies. Milkweed butterflies are a subfamily, Danainae, in the family Nymphalidae, or brush-footed butterflies. They lay their eggs on various milkweeds on which their larvae (caterpillars) feed. Historically, this group had been considered a separate family, Danaidae, and the tribes placed herein were sometimes considered distinct subfamilies in the Nymphalidae. There are some 300 species of Danainae worldwide. Most of the Danaini are found in tropical Asia and Africa, while the Ithomiini are diverse in the Neotropics. Tellervini are restricted to Australia and the Oriental region. Four species are found in North America: the Monarch Butterfly (Danaus plexippus); the Queen (Danaus gilippus); the Tropical Milkweed Butterfly (Lycorea cleobaea); and the Soldier Butterfly (or "Tropic Queen"; Danaus eresimus). The best known m

mber of this family is the Monarch butterfly. The larvae and the butterflies retain poisonous glycosides from their larval host plant, the milkweed, so they become distasteful to potential predators. These milkweed butterflies (Monarch, Queen, Soldier) eat only milkweeds (Asclepias) as larvae. This highly effective defense strategy shields them against almost all predators that soon learn to avoid these species after attempting to eat them. Another member known especially for its presence in butterfly greenhouses and live butterfly expositions is the Southeast Asian Idea leuconoe. The fossil milkweed butterfly Archaeolycorea is known from the Oligocene or Miocene Tremembe Formation of Brazil. It often assigned to tribe Danaini, specifically subtribe Euploeina, but this may not be correct. In any case, it provides evidence that the present family originated more than 20-30 million years ago.Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation,[1] but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea.[2][3] Usually, the term monsoon is used to refer to the rainy phase of a seasonally-changing pattern, although technically there is also a dry phase. The major monsoon systems of the world consist of the West African and Asia-Australian monsoons. The inclusion of the North and South American monsoons with incomplete wind reversal has been debated.[4] The term was first used in English in British India (now India, Bangladesh and Pakistan) and neighbouring countries to refer to the big seasonal winds blowing from the Bay of Bengal and Arabian Sea in the southwest bringing heavy rainfall to the area.[5][6] The south-west monsoon winds are called 'Nairutya Maarut' in India.