The Comma needs little introduction to anyone who has paid attention to the butterflies that visit their garden, well at least not in Bristol where it is certainly common.
We’ve chosen this species for a species account, not simply because it is a common visitor, but because we’ve seen more of its life cycle this year than ever before.
Unsurprisingly / thankfully, Comma butterfly biology is well understood, for most invertebrate species this is rarely the case. Just about any book on wildlife, insects or wildlife gardening will make reference to their life cycle. But just to summarise, adults overwinter as an imago (the accurate word for the adult stage) somewhere sheltered such as a dark, dry corner of a shed. We found one in our attic once. These adults will produce the first generation the following spring, laying the eggs which will develop through the caterpillar and chrysalis stage to form the new adults.
This first generation of the year will then repeat this process so that around the end of August / early September, new adults of the second generation will be formed, a small number of which will go on to survive until the following year to begin the cycle afresh. The caterpillar stage is of course key, and whilst these larvae feed on a small number of different plants, in our garden the only one we know they enjoy are nettles.
It was on the 2nd September that we noted the following caterpillar on its nettle food plant at the end of our garden. This wasn’t the first such caterpillar we recorded but this one seemed to be running a bit late. It was certainly the chunkiest and seemed to be moving slowly….with a purpose. That purpose was of course to become part of the second generation of adults who’s job would be to help ensure the following years cycle could begin anew.
And so it was, because very shortly it began to set itself up for a change of image. It spun its silky attachment and still very much conscious to its surroundings began the process of becoming an adult.
Now one thing we have learned was the obvious external change from caterpillar to chrysalis happens extremely quickly, but by no means immediately. This fella remained in the above state (more or less) for two more days, with me checking up on it frequently. On the 5th September around 11:30am we checked again to once more find no real change. However just over an hour later I glance over and immediately noticed something different…it was as if he was waiting for my back to be turned…
Nothing much changed then for several days, but then on the 11th September we noted Curtis (as we had by then named him) had a visitor. A Red Velvet Mite…
The intentions of this visitor were unknown but an hour later and it was nowhere to be seen, with no obvious harm done. Perhaps it was just passing by we thought….
Two days later on the 13th September, it was back, this time with a mate. Still though, no obvious damage, but clearly these guys were after something…
Then disaster! On the 15th September it was all over. Something, and we can only assume it was the red velvet mites, had bore a hole through the chrysalis and it was curtains for Curtis…
…and the very next day, following some moderate windy conditions over night, very little evidence was left that Curtis had ever existed.
Had things gone to plan Curtis would have emerged and soon began looking for a place to spend the winter. It turns out red velvet mites are known to predate much larger organisms than themselves, especially easy in the case of a chrysalis. The only problem they seemed to have was getting inside, but once in…
What does this mean for our garden
We have a few nettles that grow up each year at the far end of the garden. The ground was disturbed earlier this summer when a new fence was installed (thanks Pat). Soil disturbance releases nutrients which helps encourage this species which thrives in nutrient rich / low competition situations.
Lots of invertebrates make use of common nettle and we have been keen to encourage its presence, we certainly do not attempt to control it. And as we witnessed this year it can benefit a range of wildlife, in many cases indirectly as it ultimately did for the Red Velvet mites.
We were slightly surprised that a bird never spotted Curtis in his chrysalis, as he was very exposed on a nettle that had most of its sheltering foliage eaten, probably by Curtis himself. Not that it mattered in the end….
DC – 18th September 2021