Thursday, 12 May 2016

Butterfly ovum [eggs] Part one

The female Wood Whites ovum are laid on several species of plants, including Bird's-foot Trefoil, Bitter Vetch, Tufted Vetch and Meadow Vetchling. The ovum are laid singly on isolated plants rather than large clumps of these plants. They are laid anywhere from 50mm [2"] off the ground to just over 1200mm [just over 4"] depending on the time of year.

A pair of freshly laid Wood White ovum that have yet to dry.

Two very freshly laid ovum on the underside of a Bird's-foot Trefoil leaf
When the ovum finally dries they are white in colour.

A white Wood White's ovum on Meadow Vetchling
Then turning yellow after about five days.

A Wood Whites ovum having turned yellow
About 24 hours before the tiny Larva emerge from the ovum that was laid by a 1st brood Wood White female, turns a light pink in colour. This colouring of the ovum only happens with the ovum that are laid by 1st brood females.

A light pink coloured ovum, this coloration only applies to the ovum
laid by 1st brood female Wood Whites. The small black spots that are visible through
the transparent membrane/skin of the ovum are found on the larva's cheek
throughout the larval stage, and the red V shape that is also visible is the
Caterpillars mouth

However, ovum that are laid by the 2nd brood female Wood Whites, are orange 24 hours before the larva emerge. Because the membrane/skin of the ovum is transparent this is the colour of the larva inside the egg. This colouring only occurs with the ovum/larva that are laid by 2nd brood females.

A Wood White 2nd brood ovum 24 hours before the larva emerges

And finally the tiny orange 1st instar larva still inside the ovum.

The ovum of the Speckled Wood is laid on various types of common grass, including Cock's-foot and False Brome, usually in warm sheltered places with very little or no sun by females laying late summer. Eggs being laid in May can be deposited in much sunnier places than ones laid later in the season.

The ovum is white when laid and stays white for the duration of this stage, [even though they sometimes seem to have a lightish green tint to the colour of the ovum. This can be caused by light refraction] until about 24 hours before the larva emerges, when you can see the larva through the transparent membrane/skin of the ovum. Which has a black head and, a white body covered in black spots.

A speckled Wood ovum thats seems to have a slight green tinge to it,
this is most probably caused by light refraction.
A closer look at an image of the white ovum of the Speckled Wood.

And 24 hours before the tiny caterpillar emerges from the ovum.

The tiny larva is easily seen through the transparent membrane/skin of the ovum 24 hours
before emerging

This period lasts about 10-14 days depending on the time of year, whether the egg was laid in early or late summer. These times can also vary because of weather conditions, hot, cold etc.

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