Purple Haze

Heather, or Ling, Calluna vulgaris

Heather moorland

The heather moorlands in the North pennines are just about at their best now, with hundreds of acres of hillside clad in billions of tiny purple flowers. Although heather moorland looks like a uniform sea of purple there are three different species that contribute to the purple haze that shimmers on the fellside on a hot summer afternoon. Cross-leaved heath (Erica tetralix) grows in the boggier patches and flowers first, followed by bell heather (Erica cinerea) and ling or true heather (Calluna vulgaris) which both grow on drier soils. Flowers of the first two species are distinctly bell-shaped and in bell heather they’re concentrated in clusters at the shoot tips, whereas in cross-leaved heath they tend to be distributed more uniformly down the stem. The leaves of cross-leaved heath are distinctive too, arranged in whorls of four. Ling, in the close-up photograph above, is far the commonest of the three and has more densely packed, paler, smaller flowers distributed over long lengths of stem, with leaves that are tiny in comparison with the other two species. The heather moorlands of the north Pennines are skilfully managed by cyclical of burning in strips, removing the old, moribund heather. The fast-moving fire burns away the old heather without killing the roots, which then regenerate tender new shoots that are an important element in the diet of red grouse. Burning in strips creates a varied habitat with a mosaic of age structures, providing a habitat for a wonderful range of birds, insects and reptiles............more of them anon.

Bedeguar Galls

The strange object in the upper image, looking like an alien visitor from outer space, is a young bedeguar gall caused by the gall wasp Diplolepis rosae, which lays its eggs in the dog rose host and triggers this proliferation of tissue. When fully grown, like the example in the bottom image, the core of the gall contains up to 60 chambers, each with a wasp grub inside and enclosed in a mass of mossy grown. These galls are just beginning to become conspicuous on rose bushes around here and by late September they’ll reach their full size. As winter progresses all that spectacular mossy red growth withers but the larvae inside continue to feed through the early part of the winter, pupate and hatch in May as adults that lay eggs in unopened leaf buds. A wide range of other organisms take up residence in the gall, alongside the gall causing organism. Some are inquilines – opportunist squatters that take up residence in the gall tissue - while others are parasites that lay their eggs in the Diplolepis rosae larvae. There are even parasites that attack the parasites – hyperparasites – in these complex communities. You can find more information on this gall, the insect that causes it and the ‘hangers-on’ at http://hedgerowmobile.com/Diplolepisrosa.html

Thick-headed Flies

Conops quadrifasciata pairs remain together like this for some time after mating has taken place, and take to the air in unison

Females have a more slender abdomen that's sharply curled under at the tip

The exceptional width of the male's head is visible here. Maybe it's because the female's vision is obscured by the male above, so he has to act as look-out for both of them

These flies, mimicking wasps and linked together during mating in characteristic biplane arrangement, as thick-headed flies Conops quadrifasciatus that I found in a field of ragwort in Durham. The bottom photo shows the broad head which gives these insects their common name. They’re parasites of bumblebees, laying eggs on the adult bees which are then literally eaten alive by the parasitic larvae. One study carried out in Switzerland and published in 1990 found that almost 35 per cent of workers of early bumblebee Bombus pratorum and common carder bee B. pascuorum sampled in August contained this parasite’s pupae. At this time of year there are always a lot of sleepy-looking bumblebees apparently resting on flowers and showing little sign of feeding, and many of these are likely to be suffering from parasites, including conopid fly infestations. There’s no doubt that habitat destruction has been a major factor in bumblebee decline, but it’s also true that parasite infestations can have a very significant impact on local populations too.