Tuesday, 22 August 2017

Silver saver for insects

THE newly fledged green woodpecker first appeared right at the top of the silver birch, teetering in the trimmed twigs, apparently uncertain what to do; then it was on the trunk lower down, clinging on with its specially adapted arrangement of splayed claws, two forward and two back, so that it can move up, down and sideways around the tree.

It froze as we approached; the dull green back and flecked, greyish body were a perfect camouflage in the dappled shade, the black and white markings on the head echoing the bark colours. It resumed its work as we too froze, shooting out a saliva covered tongue to lick-up the ants.

The brighter green adults are frequent visitors to the lawn, drilling into the surface to the ants’ nests. Each fledgling will consume 1.5 million ants and ant pupae brought by the parents before it must learn to feed itself.

What are the ants doing, crawling up and down this tree? They are visiting the aphids higher up, on the tender leaves and twigs, where the sap is flowing. They tap the aphids to collect the sap and carry it down to their larvae in the nest below ground, for ants, like honey bees, are truly social, with division of labour between workers, soldiers, drones and queens, with an ability to communicate, all working together for the good of the colony.

The silver birch is such a rich source of food for so many species. The flocks of blue and long-tailed tits pass through each morning to entertain during breakfast — they too are collecting aphids.

What are the aphids doing up in the tree? Sucking up the sap and giving birth asexually to a tiny aphid every few hours. As the daylight shortens they will revert to sexual reproduction and the normal insect life cycle so that the eggs or pupa can overwinter in a sheltered spot.

More pyramidal orchids stretching up to the light in the shade of plantation beside the abandoned church of St James in Bix Bottom; this church has been handsomely restored and surrounded with oak, ash and beech trees. It reminds us of the lost world of pack animals, when this was the principal route to Oxford, before the turnpike for carriages was constructed via Bix and Nettlebed.

P.S. Dear Peter Woolsey (Standard letters, July 14), the silken tent is spun by the caterpillars themselves for their own protection. They raise their temperature by basking in the sun. This accelerates their development and makes another brood possible in this season, it’s possibly a tortrix dayflying moth.

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