While thrashing a gravel pit pond on my work experience with Matt, we found the nests of some solitary bees in the ground around the pond’s bank. Solitary bees do not live in colonies and hives like other bees, such as honeybees and bumblebees, instead living along and raising their young in a single nest. There are over 225 different species of solitary bee in the UK alone, making it almost impossible to identify these ones, especially without having seen the bees themselves. If I were to guess what kind of bees lived here, I would say, it was a Tawny Mining Bee or a Red Mason Bee, since they are both very common, and often borrow their nests in the ground. Solitary bees often pad their nests with leaves and moss on the inside to insulate their young, and create the chambers of their nests. People can often mistake these nests for a colony, because many bees often live in the same area, since it is difficult to find an acceptable habitat, and this gives the impression that they are all living together in a single large hive.
There are two main types of solitary bees, Miners and Leaf-Cutters. The miners, like the ones we found on the bank of the pond, will dig their nests in sandy or loose soil, stock up their nests with pollen and nectar to sustain the larvae, lay their young, and then seal the nests, leaving the babies to fend for themselves until they become adult bees, and dig out of the nests. Miner bees resemble honeybees closely, but you can tell the difference by looking for the pollen baskets on the back of the bee. The solitary miner bees lack these pollen baskets. Leaf-Cutter bees, will normally build their nests in dead plant matter such as stems or shallow roots, and cut out circular pieces of leaf and petal from nearby plants in order to construct their nests. Leaf-Cutter bees in particular are excellent pollinators, and are just as important to the pollination process and colonial bees.
Unfortunately, it was too windy for the bees on the day we discovered the nests, and they would not leave to let us have a better look at them, although we know they are definitely miner bees. After thrashing the pond, we left the bees as they were.
While going pond thrashing for my work experience with Matt, the third pond Matt and I needed to thrash was a large, open pond complex in the middle of what used to be an airfield. The area had been allowed to become overgrown and turned into a nature reserve, and the pond we were thrashing had used to be a gravel pit where a large tanker had once sat. We inspected the pond for potential habitats, which we would thrash to find the invertebrates in the pond. We found that the pond was filled with a pond weed called Crassula Helmsii, or New Zealand Pygmyweed, which is a highly invasive species that has taken over many ponds in Britain and killed of other pond flora. The far bank there is a large area of open water, free from pond weeds, and home to many of the smaller water beetles within the pond. It was easy to thrash this area of the pond, since it wasn’t strangled by Pygmyweed, and by stirring up the mud and slit beneath the surface of the water, we easily brought up a number of beetles.
On the far left there was an area that became shallow and clogged with mud, that made it difficult to thrash, and contained various tiny larvae, such as fly and mosquito young and bloodworms. Due to the difficulties we faced with the shallow mud in this pond, we used a different method to survey this habitat. This involved creating holes in the mud with our feet, so that water would flow into them, and we could use a fine sieve to pick out and organisms hiding amongst the dirt. Beyond the muddy section, just out of shot of the camera, was an area filled with Crassula, creating a swampy habitat, that many invertebrates such as boatmen larvae and backswimmers could live in, hiding under the cover of the weeds. This meant that we needed to search this area thoroughly until we could find no new species. Following thrashing the pond for nearly and hour, Matt and I had found water boatmen and their larvae, emperor dragonfly larvae, mayfly larvae, damselfly larvae, the shells of caddisly larvae, mosquito larvae, bloodworms, various water beetles, pond skaters and small pond snails. Interestingly, on the bank of the pond, we found evidence of solitary bee nests in the soft, red earth, although it was to windy for them to come out. Overall, this pond could be considered productive and diverse, with a great number of small water beetles and different larvae, although the presence of New Zealand Pygmyweed likely removed some of the diversity in the flora of this pond.
While doing pond surveys on my work experience, Matt and I arrived at a pond only to find that it was no longer there, leaving only a scattering of leaf litter and various aquatic mosses, surrounded by sedge and other plants. After the hot spring, the shallow woodland pond had dried out, and all of the invertebrates and other organisms had moved to other ponds or died out. Many ponds are temporary and will appear and disappear with the changes in the seasons, and the invertebrates in them, such as Mayflies and Caddisflies will move out to different ponds that are still around at the time, before returning when the pond refills, if it ever does. Such temporary ponds are essential to allow invertebrates and amphibians to thrive, since fish are unable to live there. This means that many species are preserved in such ponds, and the protection of these areas is essential too preserve the diverse ecology in British ponds. Unfortunately, it was not possible to survey this pond while dry, so we took a few photos of the area, and marked it down as dry when visited.
While thrashing a woodland pond for my work experience, I found several types of dragonfly larvae, including the larvae of the beautiful emperor dragonfly. In the pond Matt and I discovered three different species of dragonfly larvae, both hawkers and chasers. The hawker dragonfly on the right, can be recognised by it’s larvae’s larger, longer body, which will eventually turn into a dragonfly from one of the largest and fastest groups of dragonfly around. Hawkers generally fly well above head height, rarely settling, and diving down on prey like a hawk. They are the largest and fastest dragonfly, as well as the most prevalent type in Britain, with over seven species. I am not sure what species the larvae on the right is, but I suspect it is a Brown Dragonfly.
The chaser dragon fly in the middle, has a smaller and squatter body than the hawker’s, and will turn into a Four-Spotted or Broad-Bodied Chaser when it matures. Chasers sit on vegetation around ponds and rivers, waiting for their prey to fly past them, before taking to the air to hunt them down, giving them the name chasers.
The large dragonfly larvae on the left is that of an emperor dragonfly, which is extremely common in Britain, and can often be seen flitting around the edges of ponds, in Europe and parts of northern Africa. We can identify the larvae by the round shape of it’s head, as opposed to the more angular heads of the other larvae. It is also a hawker dragonfly, and has beautiful sky blue colourations when mature. They will prey mainly on butterflies, and other slow moving flying insects, which they dive down while they fly beneath them. They have been known to eat other species of dragonfly, particularly chasers and darters, which are slower and more vulnerable to their attacks. In the past, these dragonflies have been associated with witches and the devil, people claiming that they use their tails to sew up peoples eyes in the night. Obviously such tales are untrue and completely unfounded. The emperor dragonfly larvae pictured above is close to becoming a full adult, and will likely transform within a week, so we let him back into the water, keeping the other two larvae for identification under a microscope.
While thrashing in a woodland pond on my work experience, one of my thrashings brought up an adult diving bell spider. These peculiar spiders live among reeds and weeds in ponds from Asia to Europe, including British ponds. They are the only type of spider to live their entire life under the water, in little web ‘diving bells’ containing air. In well oxygenated water, new oxygen will diffuse down the concentration gradient into the diving bell, removing the need for the spider to ever return to the surface to collect more oxygen. This means the spider will hunt and mate within the safety of these bells, without ever having to leave. They hunt mainly small invertebrates and crustaceans, such as nymphs and fresh water shrimp, which they dart out of their bells to catch.
This particular spider is a female, which can be seen by her small size and dark colouration. Unusually for spiders, the female is much smaller than the male, who has a far more active life of hunting then the female. A male also has much lighter yellowish colours and creates far smaller bells to live in. When the spiders want to mate, the male will build a new bell near the female’s bell, and will then weave a tunnel through into the female’s area, where they will mate. Typically 40 – 50 eggs are lain, and will hatch into baby diving bell spiders, most of which will be eaten by frogs and fish.
Rather than release this spider back into the pond, Matt took it with him, since a friend of his had been looking to keep one. They are fairly challenging to keep, requiring live prey, large spaces, and well oxygenated water. These are not recommended for beginner keepers.
While pond thrashing on my work experience, Matt and I needed to thrash this woodland based pond. The first step in thrashing any pond is to locate the different habitats within the pond that might contain different organisms. After a quick search of this pond we found that there were three potential habitats. On the far left there is an open bank, where water from the pond has retreated after a particularly hot spring. There are spongy water mosses covering this bank and, out of shot, waterside plants mark where the pond used to be. On the far right side, there are large groups of bulrushes and other sedge plants. These rushes could easily provide cover for a number of invertebrates, including boatmen nymphs or mayfly larvae. These bulrushes also conceal a young willow sapling. Willow is known for destroying ponds, as the leaves it drops cause the pond to acidify and dry out. As this tree grows, this pond will likely become only a hole in the ground. At back, there is a more covered area, with several trees overhanging it. Much more leaf litter sits on the surface here, than in the other sections, and you can see gases bubbling to the surface, from the decomposition of the plant matter below. This habitat is often highly specialised, since the large amounts of decomposition, can often mean there is less oxygen in the water than most invertebrates can survive. Rat-Tail Maggots and other low oxygen creatures may live in this water, and so it is important to check this area meticulously.
After thrashing the pond for about 45 minutes, we collect a number of species, including boatmen larvae, mayfly larvae, bloodworms, leeches, several species of water beetle, caddisfly shells and pond snails. Notably we also found several types of dragonfly nymph and a diving spider. These finds indicated a productive but not very diverse pond, since it had ample amount of 1st trophic level invertebrates and top predators like hawker dragonflies.