A coppery autumn has followed a superbly sunny summer. I’ve been admiring a late, great third generation of small coppers, some of which are huge, suggesting their caterpillars thrived earlier in the year.
It is hard to declare 2018 a vintage butterfly year because the scientific data has not yet been crunched. In fact, the Big Butterfly Count suggests that this ideal butterfly weather only confirms a dismal loss of abundance. An average of 11 butterflies (of 19 common target species) per count was barely higher than 2017, the lowest in the count’s nine-year history. Particularly worrying is the small tortoiseshell’s mysterious decline.
However, this count missed the year’s earlier-than-usual butterfly peak. Species from rare (black hairstreak) to common (common blue) enjoyed superb summers. Thriving species already expanding their range (purple emperor, marbled white) popped up in more new locations. (The purple emperor also experienced its best ever year in the Netherlands.)
Sunshine sparks butterfly booms, but the ’76 drought was the most catastrophic single event for British butterflies, causing caterpillar food plants to die. This year, warm weather has created extra generations, including a second brood of chalkhill blues. Autumnal emergences can be a “developmental trap” with offspring unable to survive winter.
