’RED Admiral thrives despite wet summer’ runs a headline on Butterfly Conservation’s website. This glamorous insect is doing well in the UK, writes Richard Collins.
The first Big Butterfly Count took place there in 2010 and the census has been held annually since. 60,000 volunteer ‘citizen scientists’ took part in this year’s event. Each one downloaded a butterfly identification chart and chose a location to survey. During sessions of 15 minutes in bright weather, butterflies and day-flying moths were counted at each site.
Over 550,000 individual butterflies and moths, of 20 species, were counted in July and August this year. The average number seen, per 15-minute session, was 10.9, compared to 12.2 in 2016. Numbers have been falling since 2013, but this summer was one of the wettest in the UK for a hundred years.
Some species fared better than others. The number of the commoner ‘white’ butterflies was down by 38% and there has there been no improvement in the fortunes of the small tortoiseshell, a species which, the organisers note, “has been the source of much concern over the past decade or so”.
But several species bucked the trend. Gatekeepers, common blues, and small coppers fared very badly in 2016. Their numbers increased in 2017, although “their populations weren’t particularly large, compared with some previous years”. Comma numbers were up by 90% on 2016. But the species singled out for attention by the organisers is the red admiral; with 73,000 records, more members of this species were counted in 2017 than in the three previous annual surveys combined. It did particularly well, according to the report, in Northern Ireland and Scotland.
Purists might question the results of such an approach. However, Emily Dennis, of Kent University’s School of Mathematics Statistics and Actuarial Science, who examined them, says that the “citizen science data …produced comparable estimates of butterfly species abundance to data collected through standardised monitoring methods”. The organisers claim that their “count data match closely with those from more intensive, transect-style butterfly monitoring”.
Despite its name, the red admiral isn’t exclusively a coastal species, although, being migrants, many will have crossed the sea to get to these islands. The name is a corruption of ‘red admirable’, as the insect was once known. This is a largish butterfly, by Irish standards, velvety black with white patches, and orange bands on the wings and tail. A cosmopolitan species, it is found not only in Europe Asia and Africa, but also in Central America.
We marvel that birds weighing less then a one cent coin can travel here from Africa.
The red admiral, the weight of a paper clip, does likewise, although most of those arriving on our south coast in May or June are probably of French or Iberian origin. The visitors seek out plants, such as knapweed thistle and buddleia (the ‘butterfly-bush’), on which to feed. The males establish territories, three to eight metres wide. Females will mate only with territory holders. Little greenish eggs are laid on nettle leaves, the only larval food plant known to be used here. Caterpillars appear from June onwards, each one binding nettle leaves together to create a little shelter in which to pupate.
Some red admirals hibernate here, but few survive our winter. Many leave Ireland and migrate back southwards. J. M. Harding, in Discovering Irish Butterflies, says that “if you stand on Portmarnock Strand, County Dublin, or Hook Head, County Wexford, in early September, you will see red admirals flying south-eastwards over the sea”.
How such a tiny brain could support such a sophisticated lifestyle defies understanding. This little creature really is the ‘admirable’ butterfly.
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