Friday, 9 November 2012

Brave new moth

Our moths have a wide range of breeding and overwintering strategies: some overwinter as eggs, others as larvae, still others as pupae and a few as adults. These patterns are largely governed by the availability of foodplants, but are also affected by the length of time that the larva takes to grow to full size. That latter aspect will be further complicated by the nutritional content of the food and the efficiency of conversion by the larva of leaf into flesh. Some larvae mature very quickly, giving rise to the possibility of multiple generations per year, but the majority of our moths have a single generation each year. This is quite convenient for those of us who try to identify moths: we can usually eliminate some possibilities due to the month when we find specimens but, again, there are complications. Heat clearly plays a part in this cycle, and some species are bivoltine (having two generations) in the south of the country but only one in the north, and as we are warming, the interface between the univoltine populations and bivoltine populations is slowly moving further north, so identification strategies are having to change over time. Add to that the fact that some previously univoltine species are now becoming bivoltine in the south of the country, you can see that we are constantly having to reconsider matters that were previously facts, but are now merely indications or simply wrong.

The Red-green Carpet has a cycle where the larvae feed on leaves of trees during the year and then pupate to emerge around now. The adults mate and the female goes on to overwinter, but the males die off. When the new leaves arrive in springtime, the female will come out of hibernation to lay her eggs and next year's single generation will be under way. So in this case we have the unusual 'seasons' where both adults are found from September to November, but with the female also being seen in March to May.

Given the very short breeding season, I suppose it's not all that surprising that this species will fly when others refuse to endure the rain or cold, and yesterday I found this specimen on a door-frame just as we arrived back from walking the dogs:

Red-green Carpet - Chloroclysta siterata
Red-green Carpet can usually be identified by the reddish streaks that run along the wing, but these are sometimes absent, and we have to rely on other features, such as the white 'chevron' near the trailing edge. The above example is a female.


Gill said...

Beautiful, isn't she? And thanks for the fascinating "guide to moths".

Anonymous said...

Wow. Good on you sir. That is an incredible collection of wildlife images and all taken beautifully.I can only imagine the amount of research it also demands.I salute your commitment and passion and long may it continue.Best of luck.