The humble Speckled Wood
The humble Speckled Wood (Pararge aegeria) is actually a very special butterfly, especially for our family. In the UK there are five species of butterfly that overwinter as an adult, and its often one of these, such as the Small Tortoiseshell or Peacock, that people see as their first butterfly of the year. However, for us we look forward to seeing the first butterfly that has emerged from its chrysalis as a new adult and a true sign of spring being upon us. We’re lucky that our garden borders light woodland and so for us, the first “new” butterfly we see each year is a Speckled Wood.
Speckled Woods emerge in March (or occasionally in February in our increasingly warmer springs) and then pretty much last through the year in three broods until the end of October, and sometimes just in to November. In our garden, one or two emerge in March and then in mid-summer, after a lull when only one or two are seen, we may be lucky to see 12 to 15 Speckled Woods. These are mostly males, patrolling and perching in their territorial spots hoping to encounter a female. The patrolling males have only three eye-spots on their hindwings, whereas perching males have four spots. This difference is thought to be as a result of natural selection from predation by birds, with these eye-spots causing the birds to peck at the wings and do little or no harm rather than peck at the head or body and kill the butterfly. I've watched males “towering” in territorial fights only for one to be pecked at by a bird. Both males quickly disperse to hide amongst tree leaves, with one bearing a gap in their wing to mark a lucky escape!
The first brood lay eggs in spring and these hatch out to form a second brood in early summer. However this second brood lay eggs which hatch in to caterpillars that make a choice. Some will form a chrysalis and pupate over winter whereas others will emerge in the same year to form a third brood. This third brood lay eggs that hatch in to caterpillars that overwinter before pupating in spring. This makes the Speckled Wood one of the few British butterflies to overwinter in two life cycle stages, caterpillars and chrysalis. A real highlight for me is to see a female lay eggs in the garden at home, one at a time on chosen grass leaves. It’s a sign that there will be more Speckled Wood next year!
In Europe there are two main subspecies of Speckled Wood. In the UK we get the paler tircis which is largely found NE of a line from southern England down to the Aegean. SW of this line is the orangey aegeria, with intermediate forms along the transition line including a subspecies endemic to the Isles of Scilly called insula. In warmer years we get more orangey individuals in the UK, so its likely temperature plays a role in this distribution. There is a fourth subspecies found in western Scotland, P. a. oblita.
The pictures show tircis Speckled Woods in our garden and aegeria in France. I’ve seen the Scottish subspecies on trips to Glasdrum Wood and Glen Loy looking for Chequered Skippers, but never yet been to the Isles of Scilly to complete the set!