Monday, June 29, 2015

Swallowtail and Large Blue eggs

I've made a number of dedicated butterfly outings again this year. Along the way I've been able to photograph the eggs of a number of species, including two of our rarest butterflies.
The previous post related to the Swallowtail in Norfolk. During that same trip, hours before finding any actual butterflies, we came across the eggs of the Swallowtail. In Norfolk, the swallowtail lays its eggs on milk parsley as this is the sole food plant of the caterpillar in Norfolk.
The Large Blue is single brooded with adults flying from mid-June until late July. Eggs are laid on the young flower buds of Wild Thyme. The larvae subsequently burrow into the flower head to feed on the flowers and developing seeds. Females lay eggs on plants growing in a range of vegetation heights, but survival is best in short turf where the host ant M.sabuleti is most abundant. When the larvae are around 4 mm long they drop to the ground and wait to be found by foraging red ants, attracting them with sweet secretions from a special 'honey' gland. The larvae are picked up by the ant and placed below ground within the brood chamber. The larvae then feed on ant grubs to achieve most of their final body weight, hibernating deep within the ant's nest. The larvae pupate in early May within the nest and the newly emerging adults have to crawl up above ground before expanding their wings.

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