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|The Mimicry of a Common Crow Caterpillar|
This shot taken at my backyard. This is a caterpillar of Common Crow Butterfly. The Common Crow (Euploea core) is a common butterfly found in South Asia. In India it is also sometimes referred to as the Common Indian Crow, and in Australia as the Australian Crow. It belongs to the Crows and Tigers subfamily of the Nymphalidae (Brushfooted butterflies).
The Common Crow is the most common representative of its genus Euploea. Like the Tigers (genus Danaus), the Crows are inedible and thus mimicked by other Indian butterflies (see Batesian mimicry). In addition, the Indian species of the Euploea genus shows another kind of mimicry, Müllerian mimicry. Accordingly, this species has been studied in greater detail than other members of its genus in India.
The Common Crow (Euploea core) is a glossy black butterfly with brown underside with white marks along the outer margins of the wing. The wingspan is about 8-9 cm and the body also has prominent white spots.
Upperside dark brown, broadly paler along terminal margins; Fore and hind wing with subterminal and terminal series of white spots; on fore wing the former more or less oval, curved inwards opposite apex, the latter series often incomplete, not reaching apex, the spots smaller; often there is a small costal spot, and very rarely a spot in apex of cell and one or more discal spots; on the hind wing the inner series of spots are elongate, the outer conical. Underside similar, but ground-colour more uniform; cell, costal and discal spots on both fore and hind wing nearly always present. Fore wing subtriangular, tornus more rounded than in E. core. Hindwing broadly ovate. Upperside dark brown, broadly paler along the terminal margins, especially on the fore wing. Fore wing with more or less incomplete and obsolescent series of subterminal and terminal small white spots, and a powdering of violaceous-white scales at apex, varying very considerably in extent from a mere trace of violaceous between the veins to a large and very conspicuous patch occupying the whole of the apex. Hind wing with a subterminal series of oval or inwardly conical and terminal series of more rounded white spots. Underside paler brown, the white spots larger, more clearly defined. Fore wing not violaceous at apex, a spot (sometimes absent) in apex of cell, and two or three discal spots. Hindwing: a spot in apex of cell, also sometimes absent, and a discal series of five small spots beyond. Antennae, head, thorax and abdomen very dark brown, and, the antennae excepted, sparsely spotted with white.
It is found in Sri Lanka, India, Myanmar and Australia.
Crow has three races:
• Race vermiculata : (India) UPF spots increase in size towards the apex.
• Race core : (North India) These spots are more or less equal or reduce in size.
• Race asela : (Sri Lanka) These spots are very small and the terminal spots vanish to the apex.
It is found everywhere in India right up into the mountains till 8000 feet. Occasionally it swarms in the low, wet, jungles of South India due to the abundance of its foodplants which are spread over three orders of plants.
on damaged parts of Indian Turnsole Heliotropium indicum in Hyderabad, India.
The butterfly, being protected by its inedibility, has a leisurely flight. It is often seen flying about shrubs and bushes in search of its host plants. It visits a large variety of flowering plant species. On hot days large numbers of these butterflies can be seen mud-puddling on wet sand. This butterfly also gathers on damaged parts of plants such as Crotalaria, Heliotropium to forage for chemicals precursors to produce pheromones.
Along with other Danaids such as the Tigers, the Common Crow is one of the most common migrating butterfly species. Males and females in equal proportions have been seen to migrate.
The Common Crow is distasteful due to chemicals extracted from the latex of the food plants consumed in their caterpillar stage. Thus protected, they fly in a leisurely manner, gliding skillfully with wings held slightly above the horizontal. This indicates its protection due to inedibility to a predator. The inexperienced predator will try attacking it, but will learn soon enough to avoid this butterfly as the alkaloids in its body cause vomiting.
The butterfly has tough, leathery wings. When attacked it shams death and oozes liquid which causes any predators to release them. The butterfly thus has the ability to recover 'miraculously' after the predator thinks it has been killed.
The protection mechanisms of the Common Crow, as of the other Danaids, and indeed of all unpalatable butterflies, result in predators learning this memorable aspect at first hand. Predators soon learn to associate the patterns and habits of the butterfly species with unpalatability and to avoid ingesting them in future.
This advantage of protection has led to a number of edible butterfly species, referred to as the mimic, evolving to resemble the inedible butterfly, which is referred to as the model. The resemblance is not only in butterfly markings, but also in behavioural and flight patterns. This form of mimicry where an edible species mimics an inedible species is called as Batesian mimicry.
The mimics can resemble the models very closely. In some cases, it requires hand examination and reference to field guides to tell them apart. The Common Crow is a good example, being mimicked by the following butterflies:
• Common Mime, Papilio clytia form dissimilis, both male and female.
• Malabar Raven, Papilio dravidarum, both male and female.
• Common Raven, Papilio castor, female.
• Great Eggfly, Hypolimnas bolina, female.
• Ceylon Palmfly, Elymnias singala male and female. (Not in India).
The genus Euploea also exhibits Müllerian mimicry. In this form of mimicry, the members of an inedible group of butterflies find it to their advantage to resemble one another so that their recognition by possible enemies is much easier. Besides this genus, the Blue Tigers (of the genus Danaus) also exhibit this form of mimicry in India.
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