Monday, 20 September 2010

Pupation of the Common Crow Caterpillar

Featured below is the pupation sequence of the caterpillar of the Common Crow Butterfly (Euploea core) .

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The caterpillar of this butterfly usually pupates on the leaves of its host plant. In this case it was a Oleander plant (Nerium oleander).

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Pupation starts when the caterpillar attaches itself by its posterior end to the underside of the leaf by means of the cremaster.

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It hangs suspended thus for several hours as the pupa is generated beneath the caterpillar skin.

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This period is accompanied by severe twisting motion as the caterpillar wriggles to accommodate its new body.

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The suddenly, its skin starts to split open just beneath its head region…

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… the underlying pupa is visible through the slit.

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The caterpillar/pupa then beginas another series of wriggling motions, which enlarge the split across its back.

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At the same time, the pupa pushes outward, causing the old caterpillar skin to ride backwards towards its posterior region.

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After a while, the pupa has almost emerged and there is more pupa than caterpillar to be visualised.

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As the old skin travels upwards, it crumples up …..

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…until finally it reaches the tail end, and is almost the size of a small fly

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…more wriggling on the part of the pupa ensues, this time in an effort to try and shrug the  fully split skin off its body.

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one final twisting movement and ….

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…finally the skin falls off, leaving a pale creamish pupa behind.

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It still hasn’t reached its final desire shape and as the pupa rests, it begins to acquire a clearly defined anterior and posterior end.

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The downward end will be the anterior end of the pupa, this is where the final adult butterfly’s head will be.

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The pupa also compresses itself to become more compact than the initial shape. The twitching motions begin to die down.

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Finally, gradually, the colour begins to change into a darker yellow colour as the pupa simultaneously hardens.

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After more time, it has taken on its final shape but the colour continues to change.

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After a few hours, the pupa acquires a few spots and shades that are visible in the final form.

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It has rained overnight and the final form is ready. However the colour of the pupa continues its change.

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The pupa will later taken on the metallic sheen that is typical of the Common crow, the darkness of which grows more as hatching time occurs.

Macro Monday .

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