Thursday, 21 July 2011

The be-witching hour

We are huddled around a moth trap on the southern margins of Thetford well after midnight, yet there is still the drone of traffic on the road to Bury. It has been a steady night so far, with a good mix of species in reasonable numbers, each drawn to the bright mercury vapour light of our traps. A low purr hints at the portable generator that provides us with the power needed for the traps, but it will only be when the fuel runs out that we become wholly aware of its intrusion into the still night. By that stage, dawn will not be far away and the passing traffic long ceased.

The strength of the light makes the darkness beyond all the more intense, our night vision gone. Moths buzz past our ears, occasionally blundering into us, pulled in by the light. You get a sense of the size of the moths as they approach, the more robust species trailing a whirr of heavy wings. We have with us some folk who are new to mothing and they are soon astounded by the colour and diversity of the moths on show. While the pink and ochre of an Elephant Hawkmoth creates a stir, it is the size of a Pine Hawkmoth that draws the most comment. This smart, but rather neutrally toned, species is a common catch in the Brecks at this time of the year, but this was not always the case.

The Pine Hawkmoth favours areas of open or mixed pine forest and is most strongly associated with the dry heaths and poor soils which have been devoted to timber production. It is the spread of these plantations that has really benefited the species. A century ago it would have been a rare vagrant here, but now Norfolk is well within its core range, a range that extends west into Dorset and north to Yorkshire. As its name suggests, the larvae of this impressive moth feed on pine trees, favouring the needles of Scots Pine. When small, the larvae lie along the length of a needle, relying on this slender camouflage for protection. They grow in a rather sluggish manner, becoming more conspicuous, before later descending to the ground where they overwinter as pupae under a carpet of moss or needles.

Adults are on the wing from May through into early August and are attracted to both light and to sweetly scented flowers. The females are initially reluctant to fly and remain on the trunks of trees where they await a male who will pair with them. The males, however, are more mobile and it is these that you tend to see in the traps.

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