Following on from his wonderful talk at our Autumn meeting in September 2011, Brian Everham, the head of the Wildlife Trust for Bedfordshire, Cambridgeshire & Northamptonshire, returned to lead a walk and talk on the invertebrates of Stourbridge Common on May 12th.
Brian prepares to lead the way
The sun broke through after days of rain and a group of 20+ members set off to gather specimens under Brian’s tutelage. We used a large insect collecting bag to sweep creatures from nettles, grass and trees. Brian identified them for us and interesting specimens were placed – unharmed — into clear plastic bags or tubes so that we could take them back to the Cambridge Museum of Technology for viewing. The Museum had kindly allowed us to use their main hall for Brian’s talk: he set up a projecting microscope and we examined the animals, with Brian often holding a spider or fly gently up to the lens so we could see better. (All captives were later freed.)
Bagging up the specimens
Many thanks to Hilary Pounsett for her notes on much of what we saw!
Among the most numerous species aside from masses of aphids were weevils, including the Hedge Mustard Weevil (long snout) and the Green Nettle Weevil (beautiful iridescent green and gold body). The Green Nettle Weevil lives as a grub and over-winters inside the stem of the nettle and then hatches out in Spring. In addition to many familiar red and black spot ladybirds, we also saw the lovely cream-spot Ladybird and a native yellow ladybird with black spots. Other sightings included the Birch Shield Beetle and the Hawthorne Shield Beetle.
The weird world of parasites also featured heavily, including the mite that causes lime tree galls and the parasitic wasp that does the same to stinging nettles, as well as the parasitic wasp that lives on a spider through five changes of skin.
A “micro moth” (nicknamed Margaret the Moth) which feeds on nettles charmed us with her feathery wingtips and hairy legs, as did a Green Lacewing with her huge eyes. Brian showed us a Click Beetle: normally they can right themselves if they land on their backs by ‘clicking’ their bodies, but this was a newly-hatched one who hadn’t worked the trick out yet!
The St. Mark’s Fly – so called because it traditionally hatches around St Mark’s Day, April 25th – was in fact on schedule, appearing in mid-May due to the modifications caused by the Gregorian calendar. This long, shiny black fly is often seen in swarms, but is harmless to humans. The Yellow Dung Fly, with its gingery ‘furred’ body, also likes to hang around in packs, often on cow pats; however, it’s easily annoyed by the presence of other insects, as we saw under the microscope.
In addition to the unfortunate spider wearing a white ‘rucksack’ (in fact a parasitic wasp), we also had an up-close viewing of a wolf spider, which does not spin webs but hunts instead (like a wolf….) and a jumping spider, which also does not spin a web, but, thanks to superior binocular vision, hunts by jumping onto flies (‘a hunting machine’ said Brian). A crab spider lived up to its name when inspected by microscope.
A water beetle revealed its ‘oxygen tank’ – an air bubble that it carries on its underside when it submerges. And our last performer was a netted slug, covered with a finger-print like pattern and moving along at a surprising clip.
Zoe with a Netted Slug
For Brian the high point of the day was the sighting of a small pale-brown beetle on a hawthorn tree. It turned out to be a leaf-beetle called Orsodacne cerasi, and while not nationally rare, it seems not to have been seen in Cambridgeshire before.
During his time at the University in 1665, Isaac Newton visited the Stourbridge Fair and is known to have bought a copy of Euclid's Elements which he used to teach himself mathematics. He is also believed to have acquired optical instruments including a pair of prisms - which he used to demonstrate that white light could be split in to the colors of the spectrum.