Today I saw several Speckled Wood (Pararge aegeria) butterflies! They usually fly from the beginning of April until the end of October – in three overlapping generations! Because they are able to overwinter in two totally separated development stages (Note 1), they have a complicated pattern of several adult flights per year.
Note 1: They enter the caterpillar stage between half May and half September. The growth speed differs significantly between them and some caterpillars grow as much as 3 times faster than others! Those will overwinter as pupae. The ones that emerge from the egg stage and become caterpillars in mid-August will spend the winter as half-grown larvae.
These butterflies are very territorial, and most of those I saw today were males engaged in battles (Note 2). This happens when one male has claimed a nice spot of sunlight that pierces through the trees and another male flies through his sunspot. Note that this only happens if the other male is of the same species, if a male of another kind of butterfly enters the spot he’s totally ignored. If a female flies through the sunspot, the male flies after and tries to mate with her. But otherwise he’ll remain in the same sunspot until the evening (he’ll follow the sunspot as it moves across the forest floor) and then spend the night high up in the trees.
Note 2: If you’ve never seen one of these battles and are now trying to picture what it looks like: to be honest, it looks kind of lame. The “resident” male flies towards the intruder, and then the pair flies upwards in a spiral pattern (no body contact). The one that keeps at it the longest wins. It’s usually over in a few seconds, but the longest documented battle between two male Speckled Wood butterflies went on for 94 minutes.
PS. One of my photos has been published on Natuurfotografie, the #1 platform for nature photography in The Netherlands and Belgium. If you can read Dutch, please take a look here.