The end of an epic journey

 We found this dead salmon, on Christmas Eve, in Waskerley beck, a tributory of the river Wear at Wolsingham in Weardale. It had evidently swum upriver from the sea to spawn in shallow gravels and died of exhaustion, old age or disease - or perhaps from all three causes. Patches of fungal disease are clearly evident on its scales. Few salmon make it back to sea after they have spawned.

It would have begun life in the river as an egg, made its way downstream to the North Sea, then spent up to four years in  the sea before returning to its home river to spawn. The end of an epic journey.

Pale tussock moth caterpillar Calliteara pudibunda

 

We found this larva of a pale tussock moth crawling along the parapet of Prebends bridge, across the river Wear, in Durham.

Everything about it warned ‘don’t touch me’. It would present a challenge for most insectivorous birds, although cuckoos, with a gizzard that can cope with irritating hairs, sometimes eat them. Those deterrents inflict discomfort on tender human flesh too; finely barbed and filled with irritating fluid, they can cause dermatitis. Calliteara pudibunda was once a notorious pest of hop fields, which might explain naturalist Gilbert White’s journal entry for October 8th. 1781, noting that  ‘ …women and children have eruptions on their hands ….after they have been employed in hop picking’.  More recently, families from London’s East End, travelling to Kent for traditional hop picking work every autumn, would have been painfully familiar with these caterpillars, that they knew as ‘hop dogs’.

Pale tussock larvae are not picky about food plants and defoliate at least a dozen broadleaved tree species, including beech, hawthorn, sycamore and lime, all well represented along this riverbank. But, out of curiosity, I offered our captive some young shoots from the hop vine that twines through our garden fence. It had a nibble but was fully fed and only interested in finding somewhere dry and secure amongst the leaf litter, where it will pupate inside a cocoon woven from recycled defensive bristles.

Hatched from an egg laid last June, this wanderer - provided it hasn’t already been parasitised by an ichneumon wasp - should survive winter, metamorphosing as a beautiful pale grey moth next spring.

Ants in the compost bin

 We've been composting garden and kitchen vegetable waste in 'Dalek' bins like this for decades, but this year was the first times that we've had one taken over by nesting black ants. 

They moved in during those unusually cold weeks of early summer, probably because the warmth of decomposition in the bins provided the only location in the garden with enough heat for them to breed.  Textbooks say that they need a temperature of 10C to become active and 20C to raise a brood.

Watching their progress in the bins has been fascinating because the temperature inside rises very rapidly when the sun comes out and falls equally rapidly on dull wet days and in the evening, so they seem to be constantly moving their brood around to the optimum positions in the bin. At one point I thought they had left, but it seemed that they just moved their larvae and pupae deeper into the compost, in a cooler part of the bin. They shift their brood with remarkable speed when I lift the lid and light floods in - they can move a couple of hundred pupae, by carrying them in their jaws, in a few minutes.

Their larvae are translucent, but as they  pupate they spin a silken coat.

Lately, winged males have started to hatch so before long a queen will take to the air, followed by a swarm of males on the nuptial flight. After mating she will start a new nest, while most of the males will become food for swifts that swoop over the garden.