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.

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