Ashdown Forest, 18 September 2011
Despite being at a family get together this weekend, I did manage to ‘survive’ and more importantly get out for a couple of walks, though these were mainly unproductive. The first, on Saturday morning, was spent trying to keep dry as the clouds opened as soon as we set off. Those of us brave or maybe foolhardy enough to continue got wet, though were invigorated after a walk of several miles on Ashdown Forest. With the rain passing by mid afternoon and the sun now shining, another walk of slightly shorter distance was taken. Sadly I could not even muster a Speckled Wood!
Sunday was slightly more productive though not on the lepidopteran front. Whilst walking along a stream edge on the forest a large (45-50 mm) green insect larva was found and photographed feeding on Common Alder
(Alnus glutinosa). I later identified this as the larva of the Large Alder Sawfly
(Cimbex connatus).
Further research has suggested that up until 1997,
C. connatus was virtually extinct in Britain having not been recorded for over 90 years, the last record prior to that having been in 1904. During the 19th century, it would appear to have been fairly widespread in southern England, having been found in Suffolk, Kent, Surrey, Sussex, Devon and Cornwall. Since July 1997, when the insect was recorded near Salisbury in Wiltshire, it has been recorded with increasing frequency throughout southern and eastern England and as far north as southeast Yorkshire, though is still classed as rare. Many recent records of
C. connatus would appear to be associated with amenity-planted Italian Alder
(Alnus cordata) in such places as supermarket car parks. It may therefore be the case that at least some of the recent records are the direct or indirect result of accidental re-introductions.
The larvae feed on alders, including
Alnus glutinosa,
Alnus incana and
Alnus cordata. Fully grown, they are about 50 mm long and have a dark dorsal stripe all the way along the body. They generally feed between July and September but may still be found as late as October. The adult insect is large with a wingspan of around 50 mm and superficially resembling a hornet.
For those who may not know, although superficially similar to lepidopteran larvae, which have three pairs of thoracic legs, five pairs or less of abdominal prolegs and a pair of anal prolegs at the rear, sawfly larvae have six or seven pairs of abdominal prolegs (as clearly shown in the picture below) in addition to the thoracic legs and anal prolegs. The exception to this are the sawfly species whose larvae live inside the leaves, twigs and timber of trees and plants where evolution has reduced the function of the legs to a point where they are virtually absent in these species.
- Large Alder Sawfly, Ashdown Forest (18 September 2011)
Lets see what the weekend brings, the forecast is looking a bit mixed.
- I know what you mean about everything looking tired, over the last few days I've seen 2 Red Admirals and 5 Whites and that's been it!
