invertebrates – Page 30

Tiger of the rails

I had been slowly making my way down the rail tracks for about half an hour before I spotted the first one of these – a Six-spotted Tiger Beetle. Metallic green and vibrantly flashy in the morning sunshine, I’m surprised I’d missed them to that point, since, even though I was somewhat distracted by the birds in the trees lining the rail bed, I had also been paying some attention to the ground, looking specifically for flowers with insects on them. The tiger beetle wasn’t at the flowers, admittedly, but it would be very hard to miss such a strikingly bright insect.

These are my favourite of the beetles. Appearance-wise, it’s easy to see why they appeal. There are many beetles, though, that are flashy, iridescent, eye-catching. The scarabs are especially known for it, as are the metallic wood borers. Many scarabs also have interesting horns or such, and long-horned beetles have outlandishly long antennae. We have some of all of these around here, but it’s the tiger that remains my favourite.

Part of it is probably just that they’re quite common, a familiar beetle of early summer, and yet I’m always pleased to spot them. They tend to frequent trails and other open areas in or adjacent to deciduous woods. I tend to associate them with successional areas, spots with many young trees and shrubs, although I don’t know if this is because it’s a favoured habitat, or just simply where I happen to be more often. I’ve never seen one down at the bird research station, nor at my parents’, but they’re fairly abundant at the station’s summer banding research site, and were along the rails here, too. They’re not that big, at not much more than 13 mm (1/2″), but still large enough to catch your eye.

The adults of this species give the critters both their common and scientific names (Cicindela sexguttata). On most individuals, they have six yellowish-white spots that rim the outside of the elytra (wing covers). The number of spots on individuals can be variable, ranging from none or two up to six or eight. In the case of this one, it has an extra two spots in the inner area of the elytra, to form eight spots total.

I think part of it is also their personality. Tiger beetles obviously don’t take their name because of any physical resemblance to the mammal of the same name, since I have yet to see a tiger that’s metallic green. Instead, their name reflects their personality, and their hunting behaviour. These beetles are predaceous, preying on other small invertebrates. They especially like ants and spiders, but anything small enough to be consumed can become prey. They move with lightning speed, using this to their advantage to snatch prey before it knows what’s hit it (much like jumping spiders do; obviously camouflage is not an effective tactic with these guys).

Maybe their fangs come in to the name, too. Look at the size of those jagged-toothed mandibles relative to the beetle’s head. These massive jaws are characteristic of the group, and are used in subduing and ingesting prey items. They also have very large eyes, which are important for spotting and tracking prey as it moves. It has excellent vision, and they’re very hard to sneak up on. The one downside to this macro lens is that it’s shortened my focal distance, so now I need to be within 6 inches of the subject to get the true macro 1:1 magnification. You get fabulous photos, but only if you can get close enough to take them. Patience is definitely required; either that, or setting your camera up pointed at a flower and waiting for the bug to come to you. Which won’t work so well for these guys.

While I watched this guy, trying to get close enough to run off a series of good, sharp-focused shots, he pounce on and ate something. It happened so quickly, and I was sufficiently distracted, that I didn’t see what it was he ate. It appeared to maybe be a small spider. Whatever it was, it had many long, thin appendages sticking out of the tiger beetle’s mouth as he chewed on it.

There are 14 species of tiger beetles in Ontario, of which the Six-spotted is probably the most common. Certainly it’s one of the most generalistic, inhabiting a wide range of habitats and ranging across a broader portion of the continent. It’s found from New England, west through southern Canada to North Dakota, and south to central Texas and Florida. Sand dunes, gravel pits and beaches are among the best places to look for some of the other species, but rocky alvars and exposed rock or dirt in meadows or fields are also good spots. Not all of them are such flashy colours; many are dull browns and patterned to blend in with the ground, making them harder to spot (and also more easily overlooked, for someone who’s not actively looking).

This guy seemed to be hungry. With his second pounce, he grabbed what appeared to be a bit of dead leaf. Eventually he dropped it, losing interest, or perhaps distracted by something else. Both adults and larvae are predaceous. Adult females mate in the spring and lay each egg in a short burrow in the ground, where, sometime in late June or July, it hatches into a worm-like grub with fangs. It digs itself a longer, vertical tunnel, which it lives in the rest of the summer. It eats similar prey to the adults, lying in wait within its tunnel for some unsuspecting insect to wander by. It spends its first winter in its tunnel as a larva, awakening in the spring once the ground warms up. Later that second summer, in August or September, it pupates within its tunnel. Although it becomes an adult that fall, it doesn’t actually emerge from its tunnel until the following spring, when it will mate and start the next generation’s 2-year cycle.

I tend to think of these guys as species of high summer, but the websites I referenced seemed to indicate they are more of a mid- to late spring species. None of them gave the lifespan of adults, but the Ontario website indicates a few can be found into fall. Some adult insects lack mouthparts to feed as an adult and die shortly after emerging and mating, but this is obviously not the case for these beetles. I’ll look forward to watching them this spring and summer as I do my surveys there and at the station’s summer site.

Rail-bed bugs

As is to be expected in just about any habitat, but especially open, sunny ones, there were lots of insects of varying types along the rail tracks. I decided to sit in front of a small patch of garlic mustard (good for something, at least) to try to snap a few photos of the creatures coming in to the flowers. It was while I was sitting here that I spotted the redstart and Yellow Warblers of yesterday. I got a few photos of them, but not of the little guys at the flowers. There was very little variety at the garlic mustard, it turned out once I sat and looked closely. In fact, the above was the most abundant insect along the tracks, and all I saw at the garlic mustard flowers. I snapped this photo just a short distance down the tracks, at some coltsfoot growing at the edge of the railbed. This is a small carpenter bee, of the genus Ceratina. Species for most insects can be very difficult to pin down, and this is no exception, however it belongs to the sub-genus Zadontomerus. These bees are solitary, making their nests in dead wood or stems. They’re pretty similar to the similarly sized and patterned sweat bees, except that the small carpenter bees have long tongues, as seen here.

Another bee I spotted along the tracks was this small mining bee. Mining bees are also usually solitary, and find or dig burrows in the ground. This one was scoping out potential nest sites, checking cavities between and under pebbles. She didn’t seem to find anything to her liking while I was watching. Female bees will collect up pollen and nectar into balls that they place in the burrows as a food source for the larvae. They lay an egg on each ball prior to sealing the burrow. Bees come out in the spring once the temperature reaches about 20 C (68 F), even sometimes while there’s some snow still on the ground, and are fairly common during this season.

While I was watching the bees, I felt something land on my head and start crawling around in my hair. Thinking it might be one of the little bees, I gingerly shook it out of my hair, and it landed on a leaf on the ground. Turned out to be a little metallic-green beetle. I tried looking this one up, but couldn’t narrow it down past leaf beetles, family Chrysomelidae. There are a number of metallic beetles in this family, but none of them seemed quite the right shape. One fairly common (and introduced) species looked like an almost match except the back is pitted, and it’s not on my little beetle. So it remains a mystery, for the time being.

This final bug is a leafhopper. This is the only one of the four that I managed to determine a species name for. This is Neokolla hieroglyphica – the hieroglyph reference coming from the interesting markings on the insect’s face. The species appears to be somewhat variable in colour, and when I spotted it it actually looked more blue than the orangey it appears here in the photo. It was just sitting on a leaf on the garlic mustard plants I was trying to get photos of the small carpenter bees from. Female leafhoppers lay their eggs in the stems of various plants. I found a journal article documenting the way this species uses goldenrod, and another page that collected the species from a crop field (though it’s possible they were attracted to goldenrod in the crop field or something). There would certainly be a lot of goldenrod along the tracks.

Other insects spotted included Cabbage White butterfly (always on the move, and so very difficult to get a photo of), quite a number of flies, and one of my favourite beetles, the star of tomorrow’s post.

Water bugs

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.

Look carefully

On Tuesday I bought myself an early birthday present. I’ve been wanting a good macro lens for a while. In the winter I got a Canon close-up lens, basically the equivalent of a magnifying glass that you screw on to your existing lens like a filter. It worked fairly well, but unfortunately the lens that I had wasn’t top quality, it was the entry-level telephoto lens that came with the camera kit bundle. Sure does me fine for a beginner DSLR-er, and the price was definitely right (next step up is megabucks, relatively speaking), but because it’s low-end the optics are soft and the photos are never crisp. Generally this can be corrected with digital sharpening in Photoshop, but with the addition of the close-up lens, which softens the image a tad more, it was really hard to get good sharp shots without a tripod and ample light.

So I’d been eyeballing a dedicated macro lens. I find macro photography fascinating, because, unlike most wildlife photography, it’s a world that we don’t ordinarily see with our unaided eye. We also tend to overlook a lot of the small stuff, and I wanted to be able to capture these things to share with others. I wanted a lens that wasn’t afraid to get in there, and that would produce good sharp photos while doing so. The answer was the Canon EF 100mm f/2.8 USM Macro (quite a mouthful of a name!). I did a lot of research, and the general consensus was that the Canon 100 was the best bang for the buck at that price level. I couldn’t find a bad review. So I bought it.

I took it out to test-drive it that afternoon, swinging by the Leslie Street Spit, which wasn’t too far out of my way. It was unfortunately quite windy, and a little cool, and I had other errands to run after, so I didn’t stay out too long. I focused on the dandelions that were growing along the edge of the parking lot and nearby path, pretty much the only wildflowers growing yet in these disturbed areas. There didn’t seem to be anything visiting them, no bees, no butterflies, no insects of any sort. Until I looked closely. There, crawling around at the base of the petals, deep within the flower head, was a teeny-tiny ant. It had a slight purple sheen to it, and its antennae were tipped with pollen. I don’t really know what it is (aside from colour and general size, ants are so similar to each other…), but it does resemble the Odorous House Ant in the Kaufman guide to insects. I gather it’s not limited to houses, despite its name, and the “Odorous” comes from its habit of emitting butyric acid, which smells of rotting coconut (presumably someone who lives where coconuts grow, and subsequently rot, would know better what this smells like).

The above fly, although also on a dandelion, was from a couple days later, when I was back at my parents’ place. It was also the only insect I found on the flowers. Like the ant, flies are difficult to identify, but this might be Cheilosia sp., a type of flower fly from the family Syrphidae.

Later that day my mom and I returned to the same pond site where we found the salamanders for another check-up visit on the status of things for a program she’s doing next week. We decided to walk down the trail through the woods a little ways, looking at the wildflowers and seeing what was blooming. We were mostly focused on the flowers, so nearly overlooked this beetle, even though it was sitting out in the open on a leaf.

It’s a click beetle, though species is uncertain. Click beetles are named after a characteristic noise they make. They have a spine on the underside of their thorax that snaps into a groove a short ways further back. It’s the snapping of this spine that produces the distinct clicking noise. The noise is primarily used to distract predators, but the spine can also be useful for flipping the beetle back right-side-up if it gets turned over. The action can be quite violent sometimes, jumping the beetle some distance into the air.

Further down the trail I stopped to photograph some trilliums and found this brightly-coloured beetle perched on the edge of a flower. I discovered, when I went to look it up in the field guide, that there are quite a number of long, narrow black beetles with red collars. This particular one had the unique characteristic of two bumps on the red thorax that made it easier to distinguish from the others, but I still had to submit the image to BugGuide.net to get an ID for it. It’s Asclera ruficollis, a beetle of the northeastern woodlands. Adults are found feeding on the pollen of wildflowers during the spring period, from March to May.

The last bug of this post was a little moth that flitted across the trail as we were walking. I tracked it a short distance off the path, where it came to rest on a dead log. If I hadn’t watched it land, though, I may have been hard-pressed to locate it again. It’s just a small moth, maybe a centimeter (half an inch), and cryptically coloured so it blends in with the wood (it looks fairly obvious here because I’ve isolated it with the camera, but believe me, it wasn’t). I think it’s a species of Pseudexentera, though I don’t really know which one. I could even be wrong on the genus. All those micros can be so tricky to ID! There just aren’t a lot of field marks on their tiny wings to reference.

Going out with my new lens in hand, I was looking for little things to photograph, but I was somewhat focused on the flowers. The lesson here: look carefully and pay attention, there’s lots out there that you can just walk right by without even noticing!

Life under a rock

Last week, after my mom and I visited the pond with the salamanders, we stopped by a little creek that was just around the corner. It’s Silver Creek, which is one of the primary tributaries of the Credit River, which itself runs into Lake Ontario. Silver Creek joins the Credit just south of Georgetown, a small town west of Toronto, not far from where my parents live. It runs north through Georgetown, passing the little hamlet of Ballinifad, to its headwaters… or I suppose it’s the other way around, running south from the headwaters, to join the Credit. Either way, it’s one of the primary creeks in my parents’ “neighbourhood”.

The Credit River was one of the rivers that was part of an Atlantic Salmon reintroduction program launched in 2006 due to the quality of its water. The salmon can occasionally be seen migrating up its Silver Creek tributary, and there are signs in areas where the creek passes under roads or through parks indicating that it’s a salmon-spawning creek. It’s a good creek for salmon, with the sort of stony bottoms that create many nooks and crannies for spawning. The same characters that make it good for salmon make it good for other aquatic invertebrates and fish.

We stopped at this beautiful stone bridge and hiked down to the water’s edge. The water comes over the waterfall above and then slows down (a little) in this broader area just before the bridge. The slower water allows creatures to move around between and under the stones where in the faster currents they would be swept away. It also allowed us to step in to the water without being knocked over or our boots filling with water. Or my mom’s boots, anyway – I stood on the bank. Mom waded in and started turning over stones while I held the net a short ways downstream.

It didn’t look like we’d caught anything at first, but as I pulled the net out of the water I could see something large moving amongst the debris. We put some water in a tub and dumped the net contents in. To our surprise, there was a lot more than we initially thought. The large moving thing turned out to be this giant crayfish… in fact, all the moving things were crayfish, of varying sizes. The biggest one was dark, and very big. I can’t believe I didn’t see it go into the net when Mom turned over the stone. Mom decided she didn’t really want to lift up any more rocks.

In contrast, the little guys were quite little, perhaps only 1.5cm (less than 3/4″). There are about 500 species of crayfish in the world, about 350 of which occur in North America, where they’re also called crawfish or crawdad. I had no idea there were so many species of them. The largest is found in Tasmania and may grow up to 40cm (15.5″), the smallest is in the southeastern US and only reaches 2.5cm (1″). On average, most species grow to about 7-8cm (2.5-3″), sometimes reaching 12cm. Our big one was definitely one of the larger guys.

So I don’t know if what I had in the tub were different species or just different life stages. McMaster University lists 9 species occurring in Ontario, of which 6 are stream-dwellers. Many species will reach sexual maturity and mate the fall after they hatch, though fertilization (the female holds the sperm internally over the winter) and egg-laying usually occur in the spring. The female carries the eggs attached to her belly until they hatch 2-20 weeks later (what a time span! I assume that to be a range across species, although water temperature is also a factor). The young stay on the female till after their second moult. A crayfish lives on average about two years.

Crayfish are crustaceans, closely related to lobsters, and are in fact eaten in much of the world. In the US, they’re mostly found on plates in the southeast, prepared similarly to the lobster. Wikipedia makes the interesting observation, “Notably, in Canada the crawdad is considered interchangeable with the potato.” You know… this one seems to have slipped my observation. I use potatoes.

They’re also occasionally found as pets in aquariums. They’re easy to keep, feeding on shrimp pellets, tropical fish food, algae wafers, or other easy sources. They’re also not opposed to taking small fish if the opportunity arises, and may deplete an aquarium’s community rather quickly. Most Ontario species eat small invertebrates or fresh vegetation.

The eyes of a crayfish are on movable stalks that they manipulate to look around, rather than moving the eyeball (or the retina, like the jumping spider). They have two pairs of antennae, which they use for sensing their environment. They breathe through gills that are located on their frontmost legs (which are also used for manipulating food, and are in front of even their large pinchers); you can see them poking out from under his chin here.

After examining our catch and marveling at the size of the big guy, we gently released them back into the water to carry on with what they were doing. Which was probably sitting under a rock waiting for food to float by.