Friday, October 21, 2011

A Look beneath the Surface

This past summer I've made an effort to focus on visiting an assortment of our local wetland habitats and photographing their denizens (with an emphasis on odonates). As my camera is ill suited to underwater photography the subject matter is heavily weighted in favour of what lives in the vicinity of, or on the surface of, the waterways, thereby overlooking all the fascinating living things which make the water itself their home.

A metal sieve works best for sifting through debris that has collected in still pools of water; nylon or fibre mesh insect nets tend to snag and tear on sticks and rocks. Since it's autumn and much of the aforementioned debris is fallen leaves, it's not surprising that on my first couple of tries I dredged up some very leaf and stick-like insects. All three insects are true bugs, members of the order Hemiptera, with the piercing/sucking mouth parts typical of this group, and can bite if handled carelessly. And all three species are predacious, with raptorial front legs. More good reasons to sift the detritus with a sieve rather than one's fingers.

Left: Water Scorpion (sometimes called a Water Stick) ... Ranatra sp.
Center: Water Scorpion ... Nepa sp.
Right: Giant Water Bug ... Belostoma sp.

A couple of the stick-like Water Scorpions (Ranatra sp.): removing these insects from the water to take pictures didn't cause them any harm or distress. All of these bugs are air breathers, have fully functional wings and can easily fly to a new pool if their current home dries up, or in order to colonize new habitats. And despite the appellation "scorpion" the filaments at the end of the abdomen are harmless, they serve as breathing tubes.

A much more foliform – meaning leaf-like – Water Scorpion (Nepa sp.) in its aquatic abode.

Ventral and dorsal views of Nepa sp. It's interesting to observe the differences in behavior between the two water scorpion species. Not long after they were out of the water the two Ranatra became very active and blew their cover as "sticks". But when removed from its watery element, this insect refused to budge or twitch and did its best to behave like a dead leaf.

Another dead leaf mimic: this species of Giant Water Bug (Belostoma sp.) is only about 25 mm long, much smaller than its cousin Lethocerus americanus, which can attain twice this length.

Whenever possible it's preferable to photograph animals in their natural element. However, in the case of aquatic subjects glare reflected from the surface of the water can present a problem. Furthermore, the survival of many water dwellers depends on their ability to swim – fast – and they generally refuse co-operate and pose to have their picture taken. Moving this Fishfly larva (Chauliodes sp.) to a dry place was no solution ... it just lay on the rock, looking very much like a slug.

A small plastic container with a bit of water in the bottom served to confine the insect. However, I still had to work around glare and reflections, and for my next trip I'm going to try to a vessel that's off-white in order to produce a more neutral, less contrasting background.

Judging by the jaws I would have thought that the larval form of Chauliodes is carnivorous, but it appears that they will also consume vegetable matter and detritus.

The container also proved handy for temporarily constraining these isopods. Quite common in the submerged litter, these little freshwater crustaceans belong to the same order as the more familiar sowbugs, pillbugs and woodlice they so closely resemble. The best I could do in terms of an I.D. is family Asellidae (nor do I have any idea what kind of a worm that is in the second photo – it looks like an earthworm).

Saving the best (or perhaps the weirdest) for last: at first I mistook this peculiar looking wad of gray slime for a ... well, a wad of gray slime. It's actually an insect larva called a Rat-tailed Maggot, and will go through some rather dramatic changes on its way to adulthood; here's an image of the adult: Eristalis sp. Truth is indeed often stranger than fiction ...