There were mixed fortunes for the special wildlife of Glapthorn Cow Pastures this spring. While the black hairstreak butterflies have been abundant among the blackthorns, the fluty and trilling tones of the nightingales were absent for the second consecutive year.
Although these are the star turns of the wood, the summery rides thrum with a wide range of wildlife. Dark and speckled bush crickets hop and clamber in the deep grass that fills the open spaces. Little silk tepees are the motherly work of nursery web spiders, protection for their cream-coloured egg sacs. If the mothers are still on guard they are discreetly secreted away as the inside of the tents fill with little grey hatchlings.
Under a piece of bark hangs an even more elaborate bit of spider mother-care, a great lantern spider (Agroeca brunnea) egg sac. This exquisite little construction is the shape of an upside-down wine glass. The pea-sized egg sac is first swathed tightly in white silk and then meticulously coated with a perfect layer of greyish mud.
White sprays of richly perfumed meadowsweet leap from the ride edges and behind them mounds of bramble are laden with pink blossom. Large numbers of marmalade hoverflies (Episyrphus balteatus) drift between the flowers. These are immigrants: every summer clouds of a few species of hoverfly travel north through the continent, and this is the best year for them for some time. Buglife’s vice president, Alan Stubbs, monitors their numbers daily in his Peterborough garden; his all-time record is of more than 1,000 hoverflies, but one day this month he counted 850 individuals, of which 800 were marmalades.
The hoverfly’s ecological importance has been revealed by researchers at Exeter University and Hoverfly Recording Scheme colleagues, who have calculated that about 4bn of them move around above southern Britain, making up an incredible 80 tons of biomass (perhaps more this year). The spring influx of 700m insects brings nutrients and pollen (10 grains per fly) into the UK; their progeny will consume up to 10tn aphids – 900,000 per hectare – and make billions of flower visits, before 1.8bn fly back over the Channel in August.
