Green-veined whites 'puddling'

We came across this group of 'puddling' green-veined whites - four of about a dozen - when we were out walking on moorland near Blanchland in Northumberland last week. Each was busy sucking up moisture through its extended proboscis from rapidly drying puddles in the sand soil.

Butterfly 'puddling' is behaviour that's most often seen in wildlife documentaries, with swarms of tropical butterflies congregating around the edge of waterholes, but it's common in our butterflies too. They are sucking up a dilute solution of mineral salts, particularly sodium salts, which is essential for their reproductive success. Males hatch from the chrysalis with a fixed amount of sodium in their bodies and lose some every time they mate, so the longer they live and the more often they mate, the more they need to 'puddle' - otherwise their fertility declines.

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An amazing harvestman from Morocco

A lot of exotic animals tend to reach our shores these days and when they do they often make lurid newspaper headlines, with scare stories about 'alien invaders' that threaten our native flora and fauna. But there is one alien invader from Morocco that slipped ashore in Bournemouth almost 60 years ago, in 1957, and has steadily conquered the whole of Britain. This extraordinary harvestman, called Dicranopalpus ramosus, reached the Scottish border in 2000 and is still heading north. 

Here's one that lives on the door frame of our greenhouse. Its globular body is only about 4mm. long but its legs are proportionately enormous - they stretch almost from top to bottom of the image above. And because they are all held out at right angles to the body (aligned with the door frame above) the anmials is quite hard to spot unless it moves.

Here it is a little closer, seen from behind and showing less than half of the length of the second pair of legs, which are the longest.

The other distinctive feature of this amazing arthropod is the pair of long, forked pedipalps carried in front of the head .......

That look a little like crab claws and ......

..... are quite menacing, although they are primarily sensory structures - the jaws lie between them, under the front of the head.

When you give Dicranopalpus a gentle poke it abandons its cryptic behaviour and rises up on its splayed legs, much like any other harvestman. If you look carefully at the image above you can see the full extent of one of the second pair of legs, stretched out in front, towards the bottom of the picture.

Here you can see the fine covering of sensory hairs on one branch of those forked pedipalps and also the paired eyes carried on a turret on top of the animal, giving it all-round vision, although harvestmen have rather poor eyesight - their senses of taste, touch and scent, localised on the pedipalps and that second pair of extra-long legs, are far more acute.

So there you have it - the Moroccan invader that conquered Britain, almost unnoticed except by those who take pleasure in finding and watching this obscure but extraordinary group of animals. This is the first one I've seen - I'd never have noticed it if it hadn't moved when I shut the greenhouse door.

They are quite common now in most of Britain, apparently. They're probably in your garage, shed, greenhouse of garden right now.

For more about harvestmen, click here

Cinnabar moths and ragwort

The spread of cinnabar moths near Durham city has continued unabated this year. These moths were, until recently, uncommon in County Durham, especially away from the coast, but over the course of five years have spread from a single field to many, even when these have been separated by woodland. This year there were thousands of their stripy caterpillars on their ragwort food plant.

Livestock owners tend to detest ragwort, in cinnabar caterpillar's food source, because it can be toxic to horses and cattle. There's a very lively discussion of the pros and cons of the plant appended to Rob Yarham's thought-provoking Guardian Country Diary today.