Wednesday, 11 June 2014

To Catesby Tunnel

I took a stroll today, 11 June, 2014, to the southern entrance of the Catesby Tunnel. My real objective was Steppington Spinney at SP533568 (see blog for 4 April) but I couldn't resist having a look at this famous railway feature.

Strictly speaking I was trespassing by going on the site of the old track but hey, live dangerously! In fact the interior of the tunnel may well be dangerous, but there was no chance of actually entering. As can be seen, the entrance is firmly secured and the scene is rather sad. It is difficult now to visualise a huge 2-10-0 freight locomotive, bursting from the tunnel in a cloud of steam, hauling its wagons of coal and heading on towards London.

The southern entrance to Catesby Tunnel.
11 June, 2014

The statistics for the construction are staggering:  the tunnel was 2997 yards long and involved the removal of 290,000 cubic yards of material; 30 million bricks were used - all to placate the local landowner, a Mr Attenborough, who didn't want his peace disturbed. The quality of the engineering was apparently superb. The tunnel was built for the Great Central Railway, the last major line to be constructed out of London. 

The last train to use the tunnel passed through on 3 September, 1966, but since then schemes have been put forward to re-open the line. In 1997 the Chiltern Railways Evergreen project looked at the feasibility of the whole thing but nothing came of it.

Many sections of the old line now form a fine range of wildlife habitats, with the cuttings being particularly rich in insects and other invertebrates. By the time I reached Steppington Spinney, just to the west of the tunnel entrance, I had used up nearly all my time, having been sidetracked by interesting species.

I swished my net through the lower branches of an oak tree and almost immediately caught the whiff of a bug. An investigation showed that it was a Forest Bug, Pentatoma rufipes. In fact the tree yielded several of these insects but I replaced them on the foliage as carefully as possible. Most true bugs release a pungent odour when alarmed; it is instantly recognisable!

Final instar Forest Bug swept from oak near Charwelton.
11 June, 2014

The adult Forest Bug is a rather attractive creature, but what I had caught was a last-instar nymph. Bugs, like some other insects, pass through several stages, known as instars, before a final moult reveals the adult with the sexual equipment to mate. The instars are not as visually pleasing.

Nettle Weevils were abundant approaching
Steppington Spinney.  11 June, 2014

Nettles bore dozens of specimens of the Nettle Weevil, Phyllobius pomaceus. After mating the females lay their eggs in such a way that the emerging larvae can feed on the roots and rhizomes (underground stems) of the nettle. This is a pretty beetle but after a while the scales which give it the blue-green coloration rub off, leaving almost black patches.

A Field Rose being visited by a couple of pollen beetles.
11 June, 2014

Some lovely roses were blooming beside the old railway track. Most were Field Roses, Rosa arvensis although a few Dog Roses, Rosa canina, were also present. The flowers were attracting a number of insects.

Clytus arietus  near Steppington Spinney
11 June 2014

A Wasp beetle, Clytus arietis, seemed to be investigating something on a thistle. This handsome species is one of the commoner of the Longhorn Beetles. Not only does it look wasp-like but it moves in a jerky manner, again reminiscent of a wasp. It is reasonable to assume that these factors afford it a measure of protection - a classic example of Batesian mimicry.

Speckled Wood in a railway cutting north of Charwelton
11 June, 2014

Disappointingly few butterflies were about but a Speckled Wood, Pararge aegeria, paused to allow me a photograph. This is, of course, a common and widespread insect and they frequently wander into my garden. As the caterpillars feed on various common grasses it has plenty of choice.

Silver-ground Carpet near Steppington Spinney
11 June, 2014

Chris saw a Cinnabar on the wing yesterday so I was on the lookout for one but although its food-plant, Ragwort, was plentiful I was out of luck. A Silver-ground Carpet, Xanthorhoe montanata, posed for me but there was little else on the wing in the blustery conditions.

Cattle had churned up the ground forcing me to watch my footing. I had prudently donned welly boots but creeping up on an insect was a challenge; wellies are not built for stealth.

 Tenthredo arcuata near Steppington
Spinney.  11 June, 2014

Sawflies are generally very tricky but a few can be recognised without too much difficulty. This one is the common Tenthredo arcuata. Sawflies are related to bees, wasps and ants, but are generally regarded as being more primitive. The genus Tenthredo gives its name to the Family Tenthredinidae (I bet you really wanted to know that!).

Yellow-spot Tortrix on the edge of Steppington
Spinney. 11 June, 2014

This micro-moth, Pseudargyrotoza conwagana is common, perhaps reflecting the fact that its food-plant, Ash, is also common. It has been given the name of Yellow-spot Tortrix; I think I can see why. It sat very nicely but, being very small, was a challenge for my camera. It is another case of a very long name for a very tiny insect.

Pyrochroa serraticornis, Common Cardinal Beetle
on the edge of Steppington
Spinney. 11 June, 2014

Over recent days the Red-headed or Common Cardinal Beetle, Pyrochroa serraticornis, has kept catching my attention. Being bright red it is obvious to birds so it must surely have a means of deterring them; a foul taste perhaps. I had just reached Steppington Spinney but has dawdled to such an extent that I didn't enter the woodland. Another time perhaps.

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