Searching for a Hairstreak in a Haystack.

25 January 2016 | Posted in Michael Blencowe , Woods Mill , Insects
Searching for a Hairstreak in a Haystack.
brown hairstreak egg / Olle Akesson

With Storm Jonas racing across The Atlantic towards us I made the most of today's calm weather by rallying my Sussex Wildlife Trust colleagues to help me to take part in a butterfly survey on our Woods Mill reserve.

Our butterflies pass through the winter in all stages of their life cycle (egg, larva, pupa and adult) and will be invisible; camouflaged against twigs, trunks or hidden underground or below the leaf litter. The brown hairstreak reverses this trend. It is invisible during the summer when, on hot August days, the adults spend all their time high in the tree tops; they are one of the most elusive butterflies in Britain. However in the winter, when the butterfly is in the egg stage of its life cycle, it is comparatively easy to find. Brown hairstreaks lay their eggs in the forks of blackthorn twigs and over the winter these tiny white eggs really stand out against the bare, dark stems. So mild winter days like today are the best time to survey for this species.

After a quick lesson in brown hairstreak ecology I took the my colleagues into a blackthorn-edged field and encouraged them to 'be the butterfly'. Thinking like a brown hairstreak is the best way to find their eggs. The females will have laid their eggs on the warmest areas of the warmest blackthorn hedges. By finding a south facing hedge that will not be in shadow in August and receives sunshine early in the day you'll increase your chance of finding an egg.

The great egg race - searching the hedges at Woods Mill.

Mike eggs-amines his prize.

The team scrambled to the hedge and carefully searched through the thorns. It wasn't too long before a shout went up. I raced over with my adjudicator's magnifying glass and confirmed that it was indeed a brown hairstreak egg. Congratulations to eagle-eyed Mike Murphy who won a crème egg for his efforts.

Life thru a (hand) lens - a brown hairstreak egg at woods mill photographed (through a hand lens) by Olle Akesson.

In total only 4 eggs were found today. This particular blackthorn hedge at Woods Mill is managed with this butterfly in mind and we usually find many more eggs than this. Sadly, the adult brown hairstreaks suffered some terrible weather with frequent downpours during their late summer 2015 flight period. This would have interfered with their opportunities to successfully meet, mate and lay eggs. As a result their eggs have been very hard to find in Sussex this winter.

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