Thursday, September 15, 2016

Sexton beetles

Thursday's Guardian Country Diary is about this sexton beetle Nicrophorus vespilloides that crossed our path when we were walking near Blanchland in Northumberland.
















Burying beetles are attracted from a long distance downwind by the smell of decaying corpses of small birds and mammals. 

They've been the subject of intense study because their behaviour is extraordinary, on several counts.

If a single male arrives at the corpse first he will begin excavating soil under it until it is buried, while emitting his own pheromone that will attract a female to join in with the enterprise.

If two males find the corpse first they will co-operate with its burial, then emit their pheromones and then become aggressive and fight over a female when she arrives.

The victorious couple will them mate, lay eggs in a crypt under the body and guard their brood against all-comers for the first two weeks of their life.
















Sexton beetles also carry small ticks that do them no harm but simply hitch a ride between corpses, where they to feed on the decaying carrion and its maggots. You can see a couple on the side of the head of this individual.



















The digging power of these beetles is astonishing. The front pair of legs are shorter and dig under the dead animal while the hind pair are longer and push the soil backwards. I have seen one completely disappear below soft woodland soil in about ten seconds.

Thursday, September 8, 2016

Parasols


These fine specimens of parasol mushroom Macrolepiota procera are currently at their best in Auckland Park, Bishop Auckland. A common species, but one of the most elegant.





Thursday, September 1, 2016

Quarry life in early autumn


Today's Guardian Country Diary is about autumn gentians and heather bees in a Weardale quarry.

Weardale is a valley full of old mines and quarries, mostly legacies of the lead industry and quarrying of the Great Limestone. Most of these are now worked-out or abandoned, like this one near Hill End at Frosterley.

From a distance it looks a bleak place, but when you take a close look there are some fascinating plants and animals here.















The bottom of the quarry is flooded, with a shallow lake and islands in the centre, surrounded on the north side with weathered rock spoil tips ...












..... and the vertical rock walls are being colonised with plants and even rowan trees.















In autumn the thin turf that covers the weathered spoil tips is covered with a tapestry of small flowers, like this eyebright and ground ivy .....



















.... and this wonderfully fragrant wild thyme. Everything that's more than about one inch high is grazed off by rabbits, except for ....













... a fabulous display of autumn gentians Gentianella amarella.













Rabbits must find these distasteful because in late August there are thousands of them in flower, unmolested. 













The short calcareous turf, well-drained and with most of its nutrients leached away by rain, seems to suit this delightful little plant.






















The quarry's other autumn speciality is its colony of heather bees Colletes succincta. These little bees are slightly smaller than a honey bee and each digs its own nest tunnel in the terraces of earth that build up where sheep make regular tracks across the spoil heaps. The bees excavate individual tunnels, where they lay their eggs and provision them with heather pollen, but they nest colonially. 













This colony has several hundred individuals, whose nest tunnels are sometimes just a few inches apart. 























Smart-looking little bees, with their ginger furry thoraxes and striped abdomens.























These bees are only around for about 3-4 weeks in late summer, when the heather comes into bloom. Their first priority is to mate and the males patrol just a few inches above the ground, intercepting the females when they come within reach. Sometimes several fall to the ground, locked together in a ball of wings and legs.













After mating the bees shuttle backwards and forwards to the heather moorland, in this case several hundred metres distant, to collect food to feed their brood when they hatch from the eggs, then cap the tunnels. Autumn rain washes away their little spoil heaps of excavated soil and all trace of them disappears.















Just a few weeks in the sun, then the rest of their life cycle is spent underground.