Birches

I made a visit earlier today to Byfield Pocket Park with the intention of continuing my survey of an adjacent patch of what had been sheep-grazed meadow. It covers no more than 1500 square metres and should be a straightforward job but it has become seriously overgrown. Furthermore there had been heavy rain overnight and the whole area, with its long grass and nettles was absolutely drenched.

I turned my attention instead to the Silver Birch trees, Betula pendula. There are between six and half a dozen  (Don't be silly. Ed.) of these in the pocket park, some doubtless planted but other probably arriving via their wind borne fruits.

There are about six birches in Byfield Pocket Park.

17 August, 2020

The fruits develop as catkins and I carefully split open and examined some of these. Tiny flies, species of Semudobia, attack the seeds within the fruit and I was pleased to find evidence of Semudobia tarda.

The seeds are frequently attacked by Semudobia species, in this case

Semudobia tarda.

The fruit should be winged, allowing the seed to be carried a considerable distance. When attacked by S. tarda the wing fails to develop. I found several fruits attacked in this way. The finding of this species was pleasing as I had already found Semudobia betulae in a nearby tree a few years ago. 

It came as no surprise when a Birch Shieldbug, Elasmostethus interstinctus, dropped into my sweep net a couple of minutes later. It very much resembles the more familiar Hawthorn Shieldbug, Acanthosoma haemorrhoidale, but is clearly smaller.

Birch Shieldbugs, surprise, surprise, are common on birches.

Byfield Pocket park, 17 August, 2020

The Silver Birches were proving to be home to several quite interesting insects and this was to be expected as the tree is native to Britain, however a birch clearly of an exotic origin was also present and had clearly been planted.

It bore no label but its white bark was peeling, making it likely to be either Betula papyrifera and B. jacquemontii.

Betula jacquemontii? Byfield Pocket Park, 17 August, 2020

The foliage isn't terribly helpful as the leaves of both species are very similar. I decided it was B. jacquemontii with the confidence in my identification, on a scale of 1 to 10, of about 1.

The leaves were of little help.

The loose bark, when peeled back, revealed a pair of Common Earwigs, Forficula auricularia, their rather straight forceps showing them to be female. (Those of the male are far more curved.)

Female earwigs have rather straight pincers. Byfield Pocket Park,

17 August, 2020

More interesting was a harvestman. The manner in which its legs were spread-eagled in a near-parallel manner showed that it was Dicranopalpus ramosus. This species, originally known from Morocco, was first found in Britain in 1970 but is now very widespread; today it was the commonest species in the pocket park. The name Dicranopalpus refers to the long apophysis on the pedipalps, giving them a forked appearance. The word ramosus also means 'branched' so here we have an example of nomenclatural tautology; there are dozens of these in biology.

Dicranopalpus ramosus on birch bark. Byfield Pocket Park,

17 August, 2020

Also swept from a birch was a specimen of the Common Furniture Beetle, Anobium punctatum. It is quickly recognised by the oddly-shaped head, sometimes described as resembling a monk's cowl. The adults do not feed but it is the larvae which bore into wood, with distinctive and catastrophic results.

If you can't find an old table or chair a birch tree will do. Anobium punctatum was

present at Byfield Pocket Park. 17 August, 2020 

A tiny black weevil, Apion simile, was present in large numbers and I have another dozen or so insects to be checked, all taken in barely half an hour. Over the seasons this figure could be at least quadrupled because I have not yet looked at aphids or the larvae of moths. The Silver Birch is graceful, tough, and a home to a great range of insects. And, incidentally, mycologists love birches too for the range of fungi it supports when dying and in death. Where would we be without it!