The Marvelous in Nature

Cattail thwacks revisited

Edit: This post was recently included in the 180th edition of Friday Ark, a weekly blog carnival focusing on animals of all sorts. You can check out the full edition at The Modulator.

One of the downsides to learning things yourself using the internet or reference books as your guide is that it’s pretty easy to mis-identify something based on poor photographs, incomplete descriptions or information, or just vague or ambiguous wording, particularly if you have a notion about what you’re expecting. In one of the posts I did mid-January, about fungus in the woods in winter, I mentioned a large, creamy, fuzzy mass I observed on the trunk of a tree that I identified as a slime mold. Well, Jennifer over at A Passion for Nature corrected me on this by (correctly) suggesting that it looked like a gypsy moth egg mass.

I went back yesterday to the same area and had another look at it. The particular one I photographed still looked and felt (to my frozen-numb hands) like a cattail thwack with no particular distinguishing characteristics (I didn’t want to try taking it apart because I don’t like to disturb). However, upon closer investigation, I started noticing more of these fuzzy blobs on nearby tree trunks, pretty much all within a few feet of the ground. Some of them had much more obvious visual characteristics that may have led me to the eggs conclusion if I’d seen them first. In the above and the first photo you can actually see the individual eggs wrapped up in all the little hairs that create the fuzzy mass (I think the first photo may actually be hatched eggs from last year? It’s hard to tell, but the dark spots are very pronounced). The hairs are made by the female moth as she’s laying her eggs, and are hypothesized to protect the eggs from potential rodent and avian predators by discouraging them from getting the hairs in their face and nostrils and irritating the skin.

Gypsy Moths aren’t native to North America (like a lot of common wildlife). Rather, they were brought over to Medford, Massachusetts in 1869 by French astronomer Leopold Trouvelot, who also had an interest in insects and was hoping to breed a sturdier, more productive silkworm. Well, like often happens, the moths escaped and it didn’t take them long to settle into the new landscape. They’re now found into eastern Canada as far north as Maine and the Maritimes, as far south as northern North Carolina, and currently west into mid-Wisconsin. When you consider the size of the insect in question, it’s a pretty good area to cover over that period.

The moth’s dispersal is also made more interesting by the fact that the female moth, the recognizable white Gypsy Moth, can’t fly. When she emerges from her pupa she’s full of eggs and way too heavy to get airborne. Male moths (which are brown) can fly, and will travel long distances to reach a female, which they detect using the broad, fluffy antennae that only males possess. These antennae are specially designed to pick up the pheromone molecules released by the female when she emerges. Near a couple of the egg masses I found pupa cases left from the female when she emerged. The cases also have hair tufts that presumably protect them the same way the hairs in the egg mass do.

Still, if the females aren’t moving, then the eggs are going to be laid near where the female emerges, which also doesn’t help much with dispersal. Instead, dispersal is carried out by the caterpillars (weird, eh? The only ones without wings). Caterpillars, during the course of their feeding, climb to the top of the tree and then spin a line of silk which they use to “balloon” on the wind over to the next tree. I can’t imagine this taking them very far, so it would be a very slow dispersal.

This photo (used with permission) is of a female caught in the act of laying an egg mass in late summer. She was found inside a porta-potty, so I can’t imagine the caterpillars would have much to eat when they hatch, but I gather Gypsy Moth females aren’t too particular about where they lay their eggs. The larvae will feed on up to 500 different species of trees, but particularly favour oak. Most of the egg masses I came across were on rough-barked tree species, primarily Black Cherry. Caterpillars hatch from their eggs in early spring, late April into early May. They feed on tree leaves and can be a severe pest in some areas where they completely denude trees of their foliage, particularly since a single egg mass can contain up to 500-1000 eggs. In late June to early July they begin to pupate, and emerge as adult moths after a couple of weeks. Females lay egg masses shortly after emerging, and adults will never eat. Adults die shortly after mating, and the species overwinters in the form of these egg masses.

It’s funny how once you know to look for something, it suddenly seems to jump out at you everywhere. Now that I’m aware of these and what they are, I’ll be keeping my eyes open for them on future walks.

The hundred-legged one

What is it about invertebrates that creeps people out so much? Cockroaches are the stereotype of unclean dwellings, and used dramatically to draw shivers from an audience, but really the insects probably have little to no interest in you personally. A spider crawling out of a drainpipe can prevent someone from stepping into a bathtub (no way was I climing in until it was taken outside or flushed down again), but the chances of it crawling on you, much less biting you, are pretty slim.

My personal insect-phobia, the one that will cause me to throw a garment into the air shrieking should I discover one hiding inside a seam, is earwigs. Creep. Me. Out. I’m not sure why, although perhaps it goes back to my childhood and having earwigs occasionally climb into clothing while it was drying on the line outside (I should note I was never bitten by one, but that didn’t reduce their creepiness). They particularly favoured the lining of bathing suits, for some reason. I’m also not terribly fond of silverfish, though that doesn’t have any childhood encounters tied to it. The rest of the groups I’m generally okay with, although spiders are better if they’re at a distance.

One guy I know revealed that he’s creeped out by leeches. Another guy said his was house centipedes, which was also my sister’s when I asked her. A couple days ago we had one of these show up in our bathroom sink (the photos in this post are of this obliging individual). I have to admit they’re fairly creepy crawlies, as creepy-crawlies go. Up to two inches long, with giant long legs that spread out in a large oval shape, long antennae and rear legs, and they can dash across a wall at lightning speed. They’ve never really bothered me, but perhaps that’s because I have all of my energy invested in earwigs.

Centipedes, unsurprisingly, get their name from their many legs (cent = hundred, pedes = feet). Millipedes also take their name from their many feet, but the “milli” means thousand. You can tell the difference between centipedes and millipedes because the former are usually flattened with just one pair of legs per body segment, while millipedes are rounded and have two pairs of legs per body segment. Millipedes have a defence mechanism of curling up into a spiral when threatened, while centipedes, which don’t have the same strong upperside, instead run away (and I challenge you to try catching one!).

There are a number of different species of centipedes in North America, but the house centipede (Scutigera coleoptrata) is the only one from the order Scutigeromorpha (the group is also called house centipedes; since the North American species is the only one on the continent, it can get away with using the group name as the species’ common name). It’s actually not even native to North America, but was instead originally from the Mediterranean and has since spread (hitching rides with humans or their cargo). It can now be found here as well as in Europe and Asia, and a few spots in Africa, Australia and New Zealand. In Japan, they’re reasonably popular and Wikipedia suggests it can often be found for sale in pet shops.

Millipedes are scavengers, eating detritus and dead material. Centipedes, including the house centipede, are predators, eating insects and arthropods commonly found in a household environment, such as spiders, ants, silverfish, cockroaches, termites and bedbugs, and as such could be considered beneficial bugs to have around. They kill their prey by injecting venom through small “fangs”, the same way spiders do. Although it is technically possible to be bitten by a house centipede, you would have to be intentionally or accidentally handling it, and even then it probably wouldn’t feel like much, as their fangs are too small to puncture most skin. The biggest house centipedes might be able to inflict a good bite if presented some soft skin, which would feel a bit like being stung by a bee, and would similarly subside after a few hours (also, a small number of people may be allergic to the centipede’s venom like some people are to bee stings).

Although they can be found almost anywhere in the house, they prefer damp locations, such as basements or bathrooms, or overwatered houseplants. Outside they can be encountered under rocks, in wood piles or in compost heaps. They’ll happily overwinter in your house, and are commonly seen in spring (or in mild spells mid-winter) when the weather begins to warm.

House centipedes start out with just four pairs of legs when they hatch, but go through a series of larval stages (“instars”) where they shed their previous exoskeleton (their hard outer shell – insects wear their skeleton on the outside and attach all their muscles to its inner surface, compared to vertebrate animals whose skeleton is inside with the muscles affixed to the outside). It may take them up to three years to reach full size, where they’ll have 15 pairs of legs (centipedes can have anywhere from 15 to 100+ pairs of legs, but the number of legs is always odd). Once full grown they can live up to seven years.

Adults have compound eyes, like many insects (though we tend to think of flies first), and so have excellent vision (also helpful, in addition to their speed, in evading capture). They’re the only group of centipedes to have this feature. They have three modified feeding appendages, “toothed” mandibles (visible in the above photo as a sort of beak-like shape under the face), a pair of maxillae, and a pair of leg-like palps (visible in the previous photo as . The mandibles “chew” the prey while the other two appendages manipulate it. The “fangs” are found on the first body segment, behind the head. I kind of think it looks like a grasshopper head, and if you couldn’t see the rest of the body you might almost believe it was related to this much less creepy crawlie group.

Time seals all wounds

This is a familiar sight on public-use trails. Something in the human nature cries out to leave a mark, something to indicate that yes, I was here. Perhaps it’s our subconscious recognition that our life is fleeting, ephemeral? Perhaps it’s lovebirds applying superstition to an emblem of their love: as long as this shall remain, so shall we. Or perhaps it’s a declaration of possession, this bit of tree belongs to the carver. Whatever the motivation, the poor trees that find themselves suddenly trail-side usually also find themselves dealing with regular wounds.

Animals, when wounded, regenerate the cells that were killed or destroyed by nearby cells of the same tissue type splitting and multiplying to take their space. If tissue has died but was not removed, the dead tissue is sloughed off or metabolized, then replaced. Trees, on the other hand, simply seal off the wound site and dead or decaying wood, and don’t have the ability to regenerate dead tissue.

Trees wounds can be caused by being scraped, eaten by animals, broken branches, fire or insect attacks. The outer layer of the tree, the bark, is effectively dead and damage to this layer doesn’t result in injury to the tree. For a tree to suffer a wound, the injury must occur to the live wood containing the tree’s food and water transport systems (called the phloem and xylem, respectively). For some species of trees, like beech or maple, the bark is often thin and easy to penetrate (which makes them great for carving your initials into), while for others, such as many pines, the bark can be much thicker.

Trees use two methods to seal a wound. The first is compartmentalization. New wood growing around the edges of the wound creates a sort of “callus”, which effectively walls off the wounded wood from the rest of the plant. This prevents decay and infection from spreading to other parts of the tree. In the above, and below, a branch was broken off at some point in the tree’s life. The large rolls at the sides of the hole is the result of the tree sealing over the wound site with “callus” wood.

In addition to sealing off the wound site, a tree will also try to prevent the spread of infection by using certain chemical and physical responses to pathogens at the wound edge (the way our immune system sends out white blood cells to attack intruders). The exact mechanisms by which a tree does this are not well understood, but often the long-term health and survival of the tree depends on how well it accomplishes this. If pathogens are able to slip past, the whole tree may become sick. As with animals, usually vigorous, healthy trees are able to ward off infection successfully.

It used to be that the use of special tars or paints were recommended to dress tree wounds, such as those from pruning, to protect them from infection and to speed “healing”. In fact, research has suggested that these dressings did little to help, and may actually hinder a tree’s ability to seal a wound, as they may prevent drying and encourage fungal growth, and may interfere with callus growth. Similarly, filling a hollow tree cavity with the intention of increasing the strength of the trunk used to be fairly common practice, but isn’t often done anymore. It’s generally accepted that a tree’s own mechanisms are more successful than ours.

This is the trunk of an arbutus, observed when I was out on Vancouver Island last summer. They’re beautiful trees, with their deep red bark and bright evergreen (but broadleaf, not needle) leaves. Their trunk is cool and silky-smooth to the touch, like a giant piece of hand-worn worrywood, it’s incredibly soothing to run your hand across. I wish we had them here. Just looking at these images and remembering makes me feel calm.

I was so intrigued by this tree, because it seemed to have an unusual method of “healing” wounds. Rather than growing in from the sides to leave a noticeable, sharp scar, like in the first photo, the arbutus almost seems to be lacking bark altogether and just keeps building up layers of wood, filling in wounds, more like how an animal would regenerate cells. Perhaps they fill in their wounds using the same method as the deciduous trees I’m used to seeing, but form smooth, uniform wood where the wound edges meet, due to the lack of rough bark. (Note, Kim, Bert and Ken were here.)

This is the end of a broken branch, after the tree has healed over the wound site. It resembles an amputated limb to me, an even more uncanny resemblance to animal healing. I tried doing a bit of research on how arbutus trees deal with wounds, but I couldn’t find anything very helpful. I will admit that I didn’t spend hours hunting for an answer, so there may be something out there I didn’t get to.

Out in the woods behind my parents’ house there’s an old fence that used to bound part of a field, a long time ago. It predates my parents’ ownership of the place, so it’s several decades old. The tree it was secured to has grown over and around the wires so now it looks like they were drilled straight through the trunk. The scarring created by the wound-sealing process as the tree grew is visible only as a thin line, so the whole thing sort of now resembles a bit in a horse’s mouth.

Blackburnian and I encountered this weird beech tree while out at the Rouge. I have no idea what has happened to its trunk, since it doesn’t seem like the usual pattern of wounding from any sort of animal or insect attack I’m familiar with. It makes me think of parched, cracked soil, but I doubt that dehydration is the cause here. Maybe a beetle or fungus infestation?

This last one is usually referred to as a “burl”, a large growth affixed to the trunk, or sometimes large branches or roots, of a tree. The cause of burls isn’t clearly understood, although it may be due to physical trauma, or insect or fungus infestation. Burls are prized as carving wood, as they have interesting grain patterns that create beautiful finished wood pieces. Check out the size of this one spotted in the Missouri Ozarks!

Make a list, check it twice

For Christmas, I got a number of books, one of which was Julie Zickefoose‘s new book, Letters From Eden. I read it in just a couple of sittings, and enjoyed every page (some day I wanna be just like Julie!). Another one I got was Good Birders Don’t Wear White. It’s a collection of “essays” by some of the country’s best-known and leading birders and naturalists. There are some good stories and advice in it, but one of them that I thought was a particularly good suggestion was submitted by Julie as well. It’s titled, “Write it down: making a calendar”.

A bunny in my mom’s garden – photo credit my mom

Many naturalists, and birders especially, are great at keeping track of what they see. Usually, however, it’s in the form of lists. Here I have my backyard list. There is my year list. This one’s my life list. Lists are great because it’s a record of what’s been seen. The more specific the list, the more useful it can be later (for instance, a list for your backyard is more useful than a list for a state or province because it’s more specific to a certain spot; not everything on your state list will be encountered in a given spot in the state). The best lists are those that are accompanied by extra information. Rather than simply being a list of names, more details are attached to each name. For instance, recording the date you first saw a particular species in your backyard, or the location that you saw a certain species in your state.

This is the basis to Julie’s suggestion. Keep a calendar of your observations. When you see the first robin of spring, write it down. When the first green frog starts to trill in the swamp, make a note. Record notable observations you have, such as a bluebird feeding babies, or a fox trotting across your backyard. If you do this over the course of a few years you start to get a very precise picture of the timing of nature. You have a great reference to refer to when you want to know when something happens, or where, or even if. There are some great online tools for tracking bird observations, the best perhaps being eBird.com (or eBird.ca for Canadians).

The Tommy Thompson Park Bird Research Station, which I currently volunteer for, has essentially created such a calendar through careful records of observations every day for five years. It’s really interesting to compare arrival dates for species to previous earliest (or latest) dates, or to look at frequency (you actually have numbers to back yourself up when you make the statement, “this is the most bluebirds I’ve ever seen in a spring!”)

My mom has lamented recently that she wishes she’d kept a journal or record of her observations. My parents have lived at the same home in the southern Ontario countryside for nearly 30 years. By now my mom has a pretty good idea of when the Red-winged Blackbirds arrive, or when the spring peepers start to sing. But it’s still a general idea when, and there’s no record of whether it’s the same as it was 30 years ago. My parents are planning on moving and were thinking to leave some nature notes, including a species list, for the new owners. Such a calendar would have been a great introduction to the home.

Look at that great bill! And those out-of-this-world eyes!

I myself have kept a very casual personal journal on some of my birding observations over recent years, going back to 2004. It’s been helpful to refer to for some things, when I saw a certain bird, or took a particular trip. This week, I looked back through it for the date the American Woodcock arrive here. I had been thinking that they should be showing up soon. I had the notion in my head that they start their dusk display flights at the end of February.

Well, I browsed through all my late-February entries, and saw no mention of it. I tried early March in case I’d written it down late. Still nothing. Finally, it twigged that I was a month early, they won’t return till late March. Sure enough, there were the entries, at the end of March.

How disappointing. But at least it saves me from trudging out through the snow at dusk this week looking for birds that aren’t there yet.

(For those who were curious, that leading photo is from a point count survey I did one spring for the bird research station. I had forgotten my pen and notepad, but handily found a bit of charred wood to make notes with; the list washed away in the next rain. Hopefully you’ll have paper available when making your lists.)

Total eclipse of the moon

Wednesday night a spectacular and beautiful total lunar eclipse took place, visible to most of the North American continent. It was, unsurprisingly, a very popular topic on blogs throughout the blogosphere yesterday, with lots of people posting photos of the event. Well, I might as well add my voice to the fray, and my photos, too, even though they’re pretty similar to just about everyone else’s.

I’m pretty sure this is the first lunar eclipse I can remember watching. I may have seen one or two before, perhaps when growing up, and have simply forgotten. In any case, I’d been thinking I should go out to watch it, but, ironically, it had slipped my mind that it was Wednesday night, caught up in a drawing I was working on. I was only reminded of it when my mom came and told me it was happening. So I missed out on the first part of the eclipse, and caught it midway through.

It was a pretty cool show. When I first stepped out it was glowing a reddish orange, with just the bottom “corner” outside the shadow. The last time I looked at it the eclipse was nearly done. It’s a shame it was so cold out, it really discouraged spending a lot of time watching if you didn’t have a good view through a window. It took me a while to get my camera setup right for long-exposure shots of a bright object. The tricky bit was figuring out how to get the mirror to lock up (the setting was buried in a second tier of the menu). I had the camera mounted on a tripod, and I’d recently bought a remote shutter release (the geek in me was excited about that purchase), but even just the slight shake as the mirror flipped up to take the photo was enough to create a blur in the image. Once I figured that out I was good to go.

I saw a lot of photos on the web, but very little explanation of what was going on as this show progressed, so I did a bit of poking around and found this informative site, which I’ll summarize. NASA also has a good page about the recent eclipse.

A lunar eclipse is caused by the moon (which has no light of its own, so simply reflects the light of the sun) passing through the earth’s shadow. The earth has two shadows, one from the sun’s direct rays, and then “thinner” shadows where the sun’s rays hit it at an angle (since the sun casts light from all points of its disc in all directions, the “lower” edge of the sun will cast light in the direction of the “upper” edge of the earth). The main shadow, from the direct rays, is called the “umbra”, and the “thinner” halo shadow surrounding it is called the “penumbra”. The penumbral eclipse is very difficult to discern with the naked eye, so all the photos and etc that you see online pretty much deal with the umbral eclipse.

The moon shows up reddish during an eclipse because the small portion of light that gets to it around the sides of the earth is bent and refracted and filtered through earth’s atmosphere, which results in only the red wavelengths hitting the moon. It’s this refraction that allows the moon to be visible during an eclipse; if earth had no atmosphere the moon would be black.

An eclipse can only occur during a full moon. It can also only occur when the moon passes directly behind the earth. Because of the way the moon orbits the earth, it’s usually offset enough that it passes above or below the earth’s umbral shadow when its orbit takes it behind the planet. This is why eclipses are so infrequent. Total eclipses, where the whole of the moon passes through the umbral shadow, are very rare, and partial eclipses, where just a portion is in shadow, are only slightly more common. Partial eclipses outnumber total eclipses 7 to 6 (not a big margin, is it?).

But infrequent is definitely a relative term. We don’t get a lunar eclipse every full moon, but it’s estimated that between 2000BC and 3000AD (a very long time-span, I’ll admit, at 5000 years and certainly outside of most people’s frame of reference), 7,718 eclipses (both partial and total) will take place. That’s about three every two years (1.5 a year). It’s possible to have up to three take place in a year. The last time that happened was in 1982.

The next total eclipse won’t happen until December of 2010. However, there will be a partial eclipse this August. Unfortunately, the Americas won’t be able to see it because it will take place while the moon is below our horizon. The next one the Americas will get to view will in fact be the 2010 total eclipse (western America will get to see a partial one earlier that year, as well). We’ll be treated to two total eclipses in both 2014 and 2015. Other parts of the world will see some that we won’t in the time in between.

Visible near the moon during this eclipse were two bright points of light. The one on the left, to the east, is Saturn, while the one to the upper right, to the west, is the bright star Regulus. I could see with my eye, but not capture with the camera, that the moon was sitting in the constellation Leo during the eclipse. The little blue crescent in the images I think is some sort of reflection or refraction from the glass of my lens. I kind of liked the effect it created, so left it in.

While I was out there messing around with long exposures and night sky shots, I tried playing with a long exposure of the stars. The length of exposure on this shot was 240 seconds, or 4 minutes. It was taken with my long lens on the camera, at about 200mm (I think). The long streaks of the stars were actually created by the earth’s rotation, you can see a bit of a branch that’s stationary. I was surprised that they would be so pronounced with such a (relatively) short exposure!

S	M	T	W	T	F	S
				1	2	3
4	5	6	7	8	9	10
11	12	13	14	15	16	17
18	19	20	21	22	23	24
25	26	27	28	29	30	31