Survivors

Yesterday I posted some pictures of the ichneumon wasp called Orthopelma mediator that parasitises Diplolepis rosae, the gall wasp that causes bedeguar galls on wild roses. Today seven more parasites hatched out, but so did two surviving D. rosae gall wasps, pictured below. Large galls, like the one I collected, can contain up to 60 D. rosae larvae.

These dumpy little wasps, about 4mm. long, have a very distinctive profile with an enlarged red abdomen that's keeled underneath.

Almost all D.rosae individuals are female and reproduce parthenogenetically, producing fertile eggs without fertilisation by males, which are rare. The female inserts her eggs in rose leaf buds just before they begin to open and the plant cells that they are attached to proliferate to produce the spectacular mossy, crimson gall, which contains a nutritive tissue that the larvae feed on.

Below are a couple of pictures of the gall produced by this little wasp

Wasps and Figwort

Somewhere in our garden - or close by - there must be a nest of these tree wasps Vespula sylvestris because they are all over the garden at the moment.

When their breeding season comes to an end the wasps concentrate of feeding themselves with anything sweet that they can find, instead of catching insects to feed the brood - and that's when they become a nuisance, entering kitchens to satisfy their craving for sweet food.

Sometimes they just seem to sit around and do nothing and that's when they are at their most menacing, because it's easy to accidentally grab one when you're weeding the garden - as I know to my cost. At least when they are flying they buzz and you can hear them coming.

Fortunately there some plants in the bog garden that divert their attention. They find figwort Scrophularia nodosa absolutely irresistible .... although they do struggle a bit to reach the nectar in the flowers .....

In order to force their heads into the flowers they have to curl their tail right underneath .....

.... and hug the flowers, but once they get a good grip on the flower they can force their wedge-shaped heads in, picking up pollen and transferring it to other flowers as they feed. I've spent quite a while watching them and, in comparison with bees, they are unmethodical flower visitors. Bees will usually move from one flower to the next-nearest one, whereas the wasps seem to forage around at random, often coming back to the same flower several times within a few minutes.  

A Tree-spotter's guide to Buds: part 3

Still bearing the fruit of last spring's blossom, this blackthorn Prunus spinosa twig with its tight little clusters of buds will be clothed in a froth of white flowers in a little over three months from now. Blackthorn flower buds are carried on short woody spurs.

The attractive buds of bird cherry Prunus padus - glossy, purple-brown and pointed. A hedgerow tree that's commonest in the northern half of Britain.

Hawthorn Crataegus monogyna with short, pointed buds and twigs that often end in the thorns that make this such an effective, stock-proof hedge.

Small greenish buds of silver birch Betula pendula, on long, slender twigs that contribute to the tree's graceful silhouette in winter

Field maple Acer campestre. The short space between the bud scale scars that girdle this twig show that it made little growth over the last two years.

The twin buds at the end of this field maple Acer campestre twig show that last year it would have carried a single flower bud that developed into a bunch of winged seeds at the end of the twig, which have since been dispersed. A bud developed on each side the the bunch of seeds, so next year this twig will branch into two.

Winter buds of oak Quercus sp. , with their small, overlapping bud scales. The bottom right bud seems to have been galled by a gall wasp, which I think may be Cynips divisa - anyone know what it is for certain? I don't think it's easy to tell from buds alone whether the tree is common oak Q. pedunculatus or sessile oak Q. petraea but a search on the ground below will sort them out: if the acorn cups have long stalks, it's the former; if the acorn cups have little or no stalk, then it's the latter.

For more posts on tree ID click here