The purpose of the visit to the pond last week was primarily to check out the creatures in the water, not the forest paths, as much as I enjoyed that. We didn’t see any of the salamanders on this trip; as plentiful as the newts had been a couple weeks ago, they were now conspicuous in their absence. In fact, there didn’t appear to be any macro-life in the pond, at least that was visible from the water’s edge. However, there was still lots of micro-life.
We scooped up a number of samples of pond water and bottom-muck, and let it settle out in a basin. Then we poked through it to see what we could find. Copepods were abundant, as well as a number of other little, microscopic creatures that were best observed with magnification. There were also quite a number of large critters, which could be observed easily (and photographed).
The above is a predaceous diving beetle, probably of the genus Neoporus. The group is also sometimes known as water tigers in their larval stages, for their predatory habit, but it also well suits this black-and-orange adult individual. Adults propel themselves with their broadly flattened hind legs, which they use as oars (but don’t confuse them with oarmen or boatmen!). I noticed while trying to get a photograph of this guy that whenever he stopped moving he’d go bottoms-up, with his head tipping forward to point toward the bottom of the tub. It was not especially helpful in getting a good photo, but this is how they collect air to breathe – in tipping forward like this they trap an air bubble underneath their wing covers which they carry with them while swimming. They’re not strictly aquatic; they can fly and will travel in order to exploit temporary water bodies.
This is the larvae of a skimmer dragonfly. Dragonfly larvae, or nymphs, are entirely aquatic during this first phase of their life. Adult dragonflies lay their eggs in the water, usually attached to vegetation, where they develop and hatch. A dragonfly spends most of its life in a larval form. Some species can remain in the water as a nymph for up to five years, depending on the species and the local environmental conditions. During this period they’ll go through more than 20 instars, or larval stages, where they moult their skin to grow. The different types of dragonflies have differently shaped larvae; the skimmers are short and squat, like this guy. Nymphs are predaceous, feeding on other invertebrates, or even sometimes small fish or tadpoles. When they’re ready to metamorphose into adults, they’ll climb up a stem out of the water, where they’ll split their skin and crawl out as an adult form. The newly emerged adult will take a few hours to strengthen up and gain its adult colours.
This is a blackfly larvae. I didn’t know what it was when I first spotted it in the water. It moves along much like an inchworm, securing one end, then moving the other, rather than crawling like a caterpillar, or wiggling like mosquito larvae. It uses suckers on its bulbous end in order to firmly attach to its substrate. If they happen to become dislodged, they remain secured to the substrate by a thin silken strand, much the way a spider that gets knocked or blown off will catch itself on a string of silk before it reaches the floor. This prevents it from getting swept away in the currents, but can also be used as a controlled way to move from one point to another within their habitat. They tend to prefer the faster-flowing segments of streams or creeks, but can be found in ponds as well. A small, leg-like appendage under the head can create a small current where none otherwise exists. They’re mostly filter-feeders, using “gills” near their head to sieve food from the water as it flows past, which is where moving water would be advantageous.
I expect that most people will recognize this bug. It’s a water strider (also known by a dozen other names of a similar theme), usually found skittering across the surface of still water such as ponds or lake edges. However, they’ll also inhabit faster moving streams, and in fact this particular one came from the creek where we caught the crayfish, although there were also some on the pond surface as well. Predatory insects, feeding on other insects and invertebrates found on or near the water surface, they can scoot across the water as fast as 1.5 m/s (nearly 5 ft/s) – per second! They need this speed to be able to catch their prey before it takes off. They’re able to stand on the water through a combination of structural and chemical water-resisting features. They have a wax covering on their legs, but the more important factor is a series of tiny hairs with grooves that line each foot and spread out the pressure of their foot on the water surface, while simultaneously trapping air between the hairs, acting a little like snowshoes combined with waterwings. At certain times of year adult striders of some species can develop with wings, which allows them to disperse from one area to the other; in other species they always have wings.
This was my favourite of all the little critters we swept up in our container. We got several of these, little tiny guys just a couple millimeters long. They sit on the water surface, much like the water striders. However, to move around, they jump like fleas. In fact, I think the name “water flea” would be much more appropriately labeled to these guys than to the microscopic Daphnia. They jump by using a mechanism similar to the click beetle in yesterday’s post. They have a long spike on their abdomen, resembling a “tail”, which is generally kept locked into place. When they want to jump, they release the clasp and the spike rapidly springs away from the body, pushing against the substrate (in this case, the water), and propelling the insect forward. It’s this jumping mechanism that gives the group its name. They can be found in nearly every habitat, even on the snow surface in winter – these ones are appropriately called “snow fleas”. Interestingly, unlike with the water striders, this speed isn’t for capturing prey, but rather for general locomotion and avoiding predators, as they’re primarily savengers, feeding on decaying plant and animal debris.
16 thoughts on “Water bugs”
I’ll have to watch for predatious diving beetles and snow fleas now. Water striders are an old friend; forty years ago they were a main reason to ignore Mum’s injunction against going down into the creek.
I didn’t know that different dragonfly groups have differently-shaped larvae. Another reason to go out mucking in the pond!
Fabulous shots. I just did a pond dipping class with my afterschool group last week. They LOVED it! (I think mostly they just like mucking around.)
Lavenderbay: Lots of neat things in there once you start poking around!
Thanks, Winterwoman. It is a great activity for kids; as you say, it’s the mucking around, but probably also the appeal of creepy-crawly things (at least with the boys).
i foud a few of these bugs in my pool and they look alot like predaceous diving beetle but it is black and dosent tip upside down it jumps when it moves but i don’t know what it is , perhaps you would know ?
Hi Waterbugfinder; I’m afraid I’m not really sure what your mystery bugs are. I know there are things called whirligig beetles that are black and move about the water surface like water striders – might those be your critters?
I saw a bug at my friends house that was in the bathroom and looks like a waterbug/ cricket…6 very long legs, kindof yellowish about 2 inch long body and hops…she says there are alot of them…my guess is that its a waterbug but we havent been able to locate a picture of this particular one. Any ideas?
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I have been bitten after swimming in a lake in the Gatineau. Any idea what we can do in order to protect oneself? These bites appeared on our bodies a few days after swimming in this lake. Can anybody help?
thank you for the information on the water strider
I photograph nature as a hobby and this was very helpful
How to get rid of water swimming bugs in an underground water tank that supplies the house with drinking water. Maybe they do the water good, I don’t know, but maybe also could get sucked into the pump and block it up. What to do.
We have these in our pool maybe 25 each time if we want to swim we have the big stick bug to how do we get rid of them