Monday, 29 June 2015

A blue tailed damselfly wash and brush up

Blue tailed damselflies (Ischnura elegans) have joined in the summer fun. It may be my imagination but they seem the shyest of the local damselflies, diminutive compared to their cousins.  Common red damselflies have an assertive flight, positively bossy in manner . They are on the wing early too and have been quartering their wetland homes for a few weeks now. Azure damselflies are also purposeful, zippy, an effect accentuated by the vivid almost all over blue of the males. The blue tails though tend to be more wary, fluttering into cover if you approach too boldly. The males are a slate grey with the blue spot at the end of their abdomen sometimes seeming to be in flying solo if the rest of the damselfly is obscured amongst the sedges and herbs. The females are even less conspicuous, although if you can sneak up close you’ll often find one flushed with a lilac thorax (the middle part of the body, bearing the wings and legs) or pale chestnut. This little male is giving himself a wipe behind his eyes before setting off on patrol, stretching his left foreleg over his head to wipe any specks from his bulbous eyes.  His blue tail spot is not fully coloured yet, but will become more intense with time. Watch out for blue specks floating through the plants around wetlands; each speck is likely to be a male blue tail, even if the rest of him is hard to see.

Friday, 12 June 2015

Sun, sex and suspicious parents: damselflies get the same hassle

Summer’s damselfies are lifting off in glittering droves. The azure damselflies (Coenagrion puella) have coloured up and the air can seem full of bright blue cocktail sticks deftly exploring the grass and rush swards, or perched up sunning themselves. Times are good in the heat. The males particularly are fidgety, landing for a few seconds then flitting up to argue. They seem unable to leave each other alone. Females tend to be cannier keeping out the way, only venturing out into public when ready to mate and provoking a rash of males to chase after them. These two are mating, the male the bluer one, the female a delicate green, hiding away  a bit in the reeds because other males will attempt to barge in, crash landing to knock them apart. Females will mate with several males. This makes life fraught for all concerned. Males endlessly pester. If a male mates with one female then unwisely abandons her another male can come in, mate and physically remove the first males sperm (I am sure you can find out how but be careful what you web search for). As a result it is much more usual for pairs to stay together for a while, the males going in for what is called mate guarding. The female uncurls from this mating wheel whilst the male maintains his hold around the back of her head with special claspers. They can fly off in this tandem, surprisingly fast. The male keeps a firm hold when they land, his legs folded, sticking up over the females head like an ornate hat whilst the female dips her abdomen into the water to lay her eggs. They still get hassled by single males, but at least they don’t have their parents turning up, unlike in the TV series

Thursday, 4 June 2015

Schrödinger’s cat, the Large Hadron Collider and Cresswell's mysterious tadpoles



Blakemoor Farm’s new field corner ponds are doing nicely. The freshly hatched tadpoles of a couple of weeks ago (see 3rd April) are now plump and assertive. They are also playing statistical games. In one of the ponds all the tadpoles are squirming together in a dense black swarm. In the next door pond they litter the sediment, scattered with a pleasing eye for complete coverage. In a third pond there are none.  Statistics are not what inspires many people’s interest in  natural history, although I know of mathematicians who have been lured into ecology on the grounds that it is much more challenging. Statistics have their uses though, especially to summarise and test observations. The trouble is when nature plays fast and loose like these tadpoles. In the first pond there are fairly simple quantitative methods that will tell you that tadpoles have a clumped distribution, whilst in the second pond that they are more or less evenly scattered about. The trouble is that the perfectly clear maths makes no sense overall because the tadpoles are doing different things in different ponds, or not turning up at all in the third pond. I doubt that the Large Hadron Collider, turned back on again today to crack even more secrets of fundamental particles, could help unravel the problem of the mathematically inconsistent tadpoles.  Tadpole uncertainty may not have the ring of quantum uncertainty or the fame of Schrödinger’s cat as a conundrum but they are a lovely mystery right on our doors step, just over a wall from the dune road.