Monday 11 July 2011

Fresh Holly blue shows its tongue

July is peak time for butterflies. What up to mid June seemed like a poor butterfly year is gearing up to a great one. Just today I watched 8 species locally. The most striking of them was this freshly emerged Holly Blue male. It is the first individual of the second generation I see this year. It basked in the morning sun in a front garden, and - unusually for this species - it sat with wings fully open for a while. Once warm, the butterfly closed its wings and fluttered onto another perch and stretched its tongue.
A more usual sitting posture for a Holly Blue, with closed wings
The butterfly with its short tongue stretched
Tongue length in butterflies is correlated with body length, so it is not surprising Lycaenids, the family to which the Holly Blue belongs, being small butterflies, have short tongues, around 8 mm. Whites and Brimstone and the Nymphalids have longer tongues, around 15 mm. For their length, some moths (such as the Hummingbird Hawkmoth) have very long tongues, 28 mm. The following table from Pollination and Floral Ecology by Pat Willmer illustrates the length differences between some butterflies and moths.
Tongue length determines the maximum depth of a flower corolla that a butterfly can take nectar from. Short tongued species prefer shallow flowers, often composite ones like brambles, tansy, hemp agrimony or dandelions.

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