Dear Readers, after a chilly couple of weeks I was delighted to see that the tadpoles are finally emerging from their spawn. What extraordinary little question marks they are! In the photo above you can see some tadpoles that are quite well grown and others, like the one with the straight tail that seems to be ‘crossing swords’ with the one above, who have just struggled out of the egg. Most of them are currently hanging around the plants, but one or two brave souls have crossed the pond to feed on the abundance of algae growing on the liner.
In the photo below I love the way that the shadows of snail and pond skater can be seen on the bottom right, while a lone tadpole keeps a very low profile. The pond skater went over to investigate the snail, but these insects are largely scavengers, who will take advantage of any invertebrate unfortunate enough to fall into the water. You might sometimes notice ‘rafts’ of pond skaters all feeding on a dead bee or clumsy fly. They have the piercing mouthparts of all bugs, and will make short work of any little corpses.
Pond skaters are superbly adapted to living on the surface of the water – their bodies and limbs are covered in tiny hairs which increase the insect’s surface area and make it easier for it to stay on the surface. If the creature is submerged by a wave (not likely on my pond where all is currently tranquil) the air bubbles trapped in the hairs will help the insect to right itself. The long middle legs are used for ‘rowing’, the back ones for steering, but to the naked eye they seem to move across the water by magic.
For pond skaters it’s all about the vibrations that they can feel through their limbs – they take a while to settle down if I walk past, even if I tiptoe. Once they’re relaxed again, you can see all sorts of shenanigans going on. Pond skaters signal to one another using different frequencies: one to repel, one as a threat, and one to signal amorous intentions. When two pond skaters notice one another, one will send out a ‘repel’ signal. If it isn’t responded to by another repel signal, or even a threat signal, the pond skater knows that it’s happened upon a female, and will send out a courtship signal. A receptive female will respond with a courtship signal, and the male will then mate and stay with her until her eggs are laid. This means that the female (who is larger than the male) will have to ferry her lover about, possibly for weeks.
When the young hatch, sometimes they will have short wings, sometimes long wings, and sometimes no wings at all. Wingless forms obviously can’t leave the water body where they were born, but this isn’t a problem if there is plenty of food – I suspect that ‘my’ pond skaters hibernated in the pond over the winter to get a head start this spring. However, if a pond gets too crowded, or dries up, it’s useful to have wings so that the young can disperse – short wings enable a local flight, long wings can carry the new pond skaters to exciting new ponds and lakes. However, this has to be balanced against the disadvantages of wings for a surface-living insect like a pond skater – wings are extra weight, and can get tangled. It’s likely that because my pond is stable and the water level is lovingly tended by a mammal (me) most of ‘my’ pond skaters will be wingless. I shall pay attention over the next few months and see what happens.
Although pond skaters in the UK are modest little chaps, the Giant Pond Skater of Vietnam (Gigantometra gigas) has a ‘legspan’ of twelve inches, and you can read all about them here.
While I was sitting on a stone with my camera trained on the pond skaters, who should pop by but Bailey King of the Cats. He is now twenty years old, and so a little bit stiff, but he is still every bit the monarch that he was previously, so much so that his minions (aka his owners) popped by to pick him up and take him home.
And finally, here is a little film of the goings on in the pond. Do not be alarmed (overly) by the appearance of two leeches from under the edge of the plant pot – this species lives by funnelling up tiny invertebrates and so the tadpoles will go unmolested.