Wednesday, 28 April 2010

First 'proper' spring butterfly on the wing

Like me, you have probably seen a few butterflies on the wing over recent weeks. These may well have included Peacock, Small Tortoiseshell, Comma and Brimstone, all of which overwinter as adults. Just possibly, you may have encountered a Red Admiral, a species which has recently demonstrated its ability to overwinter here as an adult, but which is likely to have struggled this particular year because of the severity of the weather.

Orange Tip, by MIke Toms

Our other butterflies overwinter at different stages of their life-cycle, with some spending the winter as caterpillars, others as eggs and some as pupae in a chrysalis. The Orange-tip is one of the species to spend the winter as a pupa, overwintering in tall vegetation somewhere close to the foodplants upon which it will have fed as a caterpillar; these include Cuckoo flower (Cardamine pratensis) and Garlic Mustard (Alliaria petiolata). Other foodplants are sometimes used, including garden favourites like Honesty (Lunaria annua) and Dame’s Violet (Hesperis matronalis), although the survival of the caterpillars on these plants is thought to be poor. One of the most striking things about the Orange-tip life-cycle is that although most adults emerge from pupae come spring, some are thought to delay their emergence by one or even two years. While this unusual behaviour has been recorded in captive-reared stock it has not yet, as far as I am aware, been demonstrated in the wild. One could imagine how the ability to delay emergence might be a useful survival strategy if faced by unfavourable springtime conditions.

While I am always keen to record my first Peacock or Comma of the year, I tend not to think of them as this year’s butterflies because they will have been on the wing since last autumn, visiting late season food sources to lay down the fat reserves needed to get them through the winter. This is why it is the sight of the first Orange-tip of the year that really gives me a buzz, a butterfly signal that spring is well and truly with us.

Many readers will only be aware of the male Orange-tip butterfly and will have never knowingly seen a female. This is because it is only the male that sports the orange, fingerprint smudges of colour on the wing tips that are so characteristic. Females are more subdued in their appearance and resemble our other whites, though the strongly patterned underside of the hind wing, with its grey-green splodges, is a very useful feature to look out for. Large Whites and Small Whites are also on the wing from April, so do take a closer look at any ‘small’ whites that you see in case they turn out to be a female Orange-tip.

No comments:

Post a Comment