Parenting with eight hands

Dock spider on boat

Yesterday afternoon, Blackburnian went down to the dock to check on the tarp over the boat, as it had been raining for a bit and we were concerned that the batteries that power the little electric motor might have been exposed. They weren’t, but when he pulled back the tarp from the front he exposed this spider and her nest.

It’s a dock spider, probably Dolomedes scriptus, a relatively common species. We’d noticed a little dock spider hanging about our dock over the last week. I use the word “little” in the relative sense – full-grown dock spiders are anything but little. Because of their preference for water, they are often found in association with cottages, which generally have a lot of water around. Cottages also have more people around than the average pond or stream in the woods, so the spiders are more likely to be observed. I tend to think of them as northern “cottage country” species as a result, but they are found through much of eastern North America.

Adult dock spider

The group of spiders are also known by a couple of other names: “Fishing spider”, which usually refers to members of the genus Dolomedes, or “Nursery web spider”, for the family Pisauridae. The name dock spider is obvious in its origin. Dolomedes get the name fishing spider because the spiders prey on water organisms, often water striders, but also take small minnows and tadpoles, and anything else unlucky enough to pass their way, from the water. They either lie in wait in a location above the water (such as on the dock), or they’ll stand on the water themselves, using the same mechanism as water striders to avoid being pulled under the surface. When suspended above the water they must rely on their eyesight, but by standing on the water they can use the water’s surface as a very large web and detect the vibrations of potential food sources.

Dock spider and spiderlings

The name nursery web spiders, on the other hand, comes from the parental care the spiders invest in their eggs. The female will carry the egg sac around in her chelicerae (the fang-like things at the front of her mouth) until they’re nearly ready to hatch. Then she’ll affix it somewhere and build thread over the sac. The web provides protection to the young spiderlings, as well as a substrate for them to climb on. The adult will guard the nest until the spiderlings leave about a week later.

Dock spider egg mass

The spiderlings usually hatch within 24 hours of being affixed to a surface. We discovered this firsthand, since we’d taken the boat out the night before, and when Blackburnian returned the following afternoon there was the family of spiders. He called me down to have a look. We have to assume that the spider had crawled into the crumpled tarp while we were out, and then was on the underside when the tarp was spread over the boat again, but she could also have got there on her own volition, since the boat pulls up right next to the dock.

Dock spider building nest

The female seemed, for the most part, unconcerned with my observation. Rather, she was preoccupied with fortifying the web she’d built for the spiderlings. I watched her for a little bit as she did this. She’d walk across the web trailing silk from her spinnerets. It wasn’t a single strand, like I would expect, however, but rather a fan of silk that spread out across a greater area. Much faster!

Dock spider nest threads

When she got to the edge of the nest she would affix the silk to the substrate, in this case the boat hull. I assume the glue is the same thing that makes the webs sticky, but perhaps concentrated, and also purposefully pressed onto the surface. This photo makes it look like there’s only three lines coming into each point, but there was more than that.

Dock spider spiderling

The little spiders are teensy tiny when nthey hatch, only a few millimeters, and are yellowish instead of the dark brown of their parent.. They remain in the webbing for their first week of life, then disperse off on their own. While their mother is usually not far away, the spiderlings also respond to potential danger by huddling up into a mass (based on the premise of safety in numbers).

We took the boat out again today, and weren’t sure what to do about the spiders. Eventually we decided to remove the adult, who could potentially bite if I got too close (I didn’t know, but didn’t want to take chances, either), but leave the spiderlings in their web. They seemed to deal with the experience just fine; the boat doesn’t go very fast, so they were never in wind they couldn’t hang on in. At points I noticed they’d huddle up along the rear edge of the nest, but generally they were about and moving around.

Dock spider and spiderlings

We replaced the tarp when we got back; we’ll have to see if the female returns or if the spiderlings are on their own now. Hopefully they disperse quickly – their nest is right where I like to put my legs when we’re cruising around the lake…

Why am I (still) (bird) blogging?

Baird's Sandpiper
This Baird’s Sandpiper, an uncommon-to-rare migrant in Ontario, has snagged some sort of mud-dwelling invertebrate for lunch.

July 10 marks the (approximate) three-year anniversary of I and the Bird, a blog carnival for all things birdy. Originally started by Mike of 10,000 Birds, he has hosted all three anniversary editions, as well. Each anniversary he’s challenged contributors to write on a theme. The first aniversary theme had bloggers discuss “why they bird, blog, and/or blog about birds,” while the second asked contributors “why their blogs were must-read material.” Many of the contributors who were part of those first couple of years are still writing today, and so it follows that this year’s anniversary question is “Why are you still bird blogging?”

This is an excellent question for people who have been at it for three (or more!) years. Blogging, for most people (at least the blogs I follow), is not a casual thing. Some people do have very easy-to-maintain blogs where they simply post a photo and a few words about it, or links to news stories, or such things like that. I think the majority of the nature bloggers I follow, though, spend considerably more time on their blogs than that. For instance, the average post on my blog takes me about an hour or two, depending on how much research goes into it. Even the “easy” posts, the ones where you know everything or you’re just talking about a trip you took, or that sort of thing, posts where all it takes is some image selection/editing/resizing and a bit of free association, those posts will still usually take at least half an hour start-to-finish. This is a fairly substantial time commitment that one has to make to a blog.

Hermit Thrush itching
Hermit Thrushes are over-the-wing head-scratchers – many other birds reach under the wing to their head.

My blog is young, only half a year old at this point. I think the qualifier “still” in “why am I still bird blogging?” hasn’t come to apply yet. I haven’t reached that stage that I think all bloggers inevitably go through of feeling a little tired of the time requirements involved in making frequent, thoughtful posts. The blog is still new, still fun and interesting. Who knows, perhaps it will always be that way, only time will tell. The qualifier “bird” in the question is also only loosely applied to this blog, since, while I do regularly talk about birds or bird observations, they make up only a small portion of my diverse subject matter.

I did used to update a more personal blog, one that I called my “bird journal”, which wasn’t shared with the general public but was instead mostly intended to share my birding exploits with other people I knew. I started that journal in January 2004. Initially I posted frequently to it, sometimes nearly every day. Over time, the frequency of my updates dwindled, until I was only posting once every week or two. My last post there was November 2007, after which I went into winter hiatus, when I tend to post infrequently because I’m simply not out birding a lot, and then started up this blog in the new year. The journal still exists in the blogosphere, but hasn’t been updated since.

Ruby-crowned Kinglet with bug
Ruby-crowned Kinglets eat gnats, flies, spiders, midges, and many other little bugs.

Something that this blog has that my other one didn’t is a readership. With my old journal, I had perhaps a dozen or so people who followed it regularly, nearly all friends, and I was essentially writing to them. It was a “hey, here’s what I’ve been up to lately” sort of thing, like sending out the annual letter with your Christmas cards only on a more day-to-day basis. Birding trip reports, documentation of interesting sightings, that sort of thing. I wrote to it partially to keep people updated, partially as a record for myself to look back on later. There was no sense of community in that journal. With this one I feel like I’m actually reaching out to a community of like-minded individuals.

Blackburnian and I are moving on from the research station after many good years there, and the volunteers threw us a farewell party. They’re all great people, the volunteers are, and I’m going to miss them. The party’s organizer made an informal speech about each of us, and in mine he called me a teacher; I’m a person who enjoys sharing things with others, seeing their enthusiasm about new things, watching people learn and grow. I’ve come to this realization slowly, but this is true. I love sharing information and teaching people who are likewise keen to learn and interested in the subject. In some ways I could see myself becoming a teacher, except it would need to be in a forum where all my students were there because they were interested and wanted to be, rather than in public school or such where you’ll have some students who are interested, but many more who are there just because they have to be. Perhaps someday, when I know more, I could lead nature walks or something like that.

Brown Creeper
Brown Creepers probe into bark crevices with their long beak and use their tongue to help extract hidden bugs.

The point of saying all that, though, is that that’s the reason I’m blogging. That’s the primary reason I started up this blog in the first place – it just seemed to me that there was so much cool stuff out there that you never know about till someone shares it with you, and I wanted to find it and share it. It helps that I love to write. My best friend and I have an on-going in-joke about the length of our emails (which were very rarely less than a couple thousand words). I’m sure even reading this post you can pick up on that – I could probably have summed it up in a single paragraph or less, but the words just flow out from my fingertips. Plus, I feel that any story can be summed up in a line or two, but there’s always more to the story than that, and it’s way more interesting than a single sentence can do justice to. “This is a Box Elder Bug that was laying eggs on a leaf” does accurately sum up the basic observation of this post – but aren’t the several additional paragraphs about the circumstances of its observation and its life histories and such much more interesting?

So why am I (still) (bird) blogging? To share my enthusiasm for nature and all the cool, wild, interesting, bizarre, beautiful, ugly and serene things in it. And knowing that other people are enthusiastic about and learning from what I’m writing about, too, is reward enough for me.

Another pretty alien

Dame's Rocket

Yesterday I returned for visit number four to the site I’m surveying for the City. Historically the site was a landfill for a nearby brickworks, and took the ash and brick waste from the industry. The brickworks, and therefore the landfill, were shut down in the mid-1980s. The landfill was capped and covered with clean fill, and allowed to naturalize. These days the only remainder of the site’s prior use is an old shed at the far end of the meadow, tucked into the trees at the base of the ravine slope.

Of course, the legacy of the site also lives on in the vegetation found there. Being essentially one very large disturbed site at the time it was capped some 20+ years ago, early successional, fast-growing, and introduced species are all prominent through the central open area. The surrounding slopes are predominantly mature natural forest, but through the meadow the trees consist mostly of sumac, Manitoba Maple, poplars, and young pines. The site has been part of a tree planting program the City runs, and I gather the goal is eventually to reforest the site. Interestingly, I notice a lot of the trees they’ve planted aren’t in fact forest trees, but rather shrubby stuff such as hawthorn.

Dame's Rocket

Along with the highly invasive garlic mustard that just seems to get everywhere, one of the common plants at the site is this lovely pinkish-mauve wildflower. It’s fairly common, I see it a lot in open fields, roadsides, abandoned properties, and re-naturalizing areas such as here. I didn’t really know what it was, but noting its resemblance to the phlox in my mom’s garden, I just labeled it a wild phlox.

In fact, it’s not a phlox, but this is a fairly common mistake. This is Dame’s Rocket, Hesperis matronalis, a native of Eurasia. Like so many of our introduced wildflowers, this species is a member of the mustard family, Brassicaceae. The easiest way to tell it apart from native phlox is by the number of petals: Dame’s Rocket has four (like all of the mustards), while native phlox has five.

Dame's Rocket

The plants are prolific seed-producers, and seeds are quite hardy. The plants spring up earlier in the spring than many native meadow wildflowers, which tend to bloom in the height of summer. As such, it’s not uncommon to see extensive stands of Dame’s Rocket in meadow areas. Seeds of the plant are often included in wildflower seed packages, which aids in its spread. They prefer full sun or partial shade, but can sometimes be found in open woods as well. The flowering stems are likely two-year-old plants; most plants produce only a basal rosette in their first year.

Dame's Rocket

There’s quite a variety of colour in a stand of the flower. It can vary from a deep pinkish-mauve to nearly white, with a full range in between. A few have variegated patterns on the petals. I’m not sure if this is a natural variation, or a result of gradual domestication. The flower was cultivated as a common garden plant in its native Eurasia, and brought over to North America in the 17th century for that purpose. These days it’s found scattered virtually across the continent, with the exception of the deserts and mangroves of the south, and most of the arctic tundra of the north.

Dame's Rocket

Even though it’s introduced, Dame’s Rocket does have good benefits for wildlife. It’s frequently visited by many insects such as bees and butterflies for its nectar. Seed-eating birds will eat its seeds in the fall. Even in North America there are insects whose larvae will feed on the foliage, one of the most common being the Cabbage White butterfly. I’m not sure that placing the bird house in the middle of the stand of flowers really offers the residents any benefits, but it does afford them a nice view.

Dame's Rocket

The genus name for Dame’s Rocket, Hesperis, is Greek for “evening”. The flowers of members of this group have very strong scents, which becomes much more noticeable in the evening. This strong fragrance also provides a couple of the other common names for the species: Night Scented Gilliflower, Summer Lilac, and Mother-of-the-Evening (the latter seems to imply that mothers are especially fragrant). Two other often-used names are Dame’s Violet and Sweet Rocket. I’m rather partial to “Gilliflower” myself, though.

Dame's Rocket

I seem to be featuring a lot of introduced species here. Eventually I’ll find a native one! The more I look, the more I’m amazed at how many introduced species there are. I’d be interested to know what percentage of the wildflowers we see are actually introduced, both as a proportion of species, but also a proportion of biomass. I wonder if you can find that information somewhere…

Dame's Rocket

Reaching maturity

Horse Chestnut

Time just seems to fly by. I can’t believe we’re at June already! It seemed like just yesterday the snow was melting and I was chomping at the bit for warm weather, green leaves, birds and moths. Well, they’re all here, and they seem to have snuck up on me quite unexpectedly. They say this begins to happen as you get older, but I would hardly qualify myself as such just yet – and if time flies this much at this age, I can’t imagine how it’ll be zooming in another few decades. They also say time flies when you’re having fun, so I suppose that indicates how I’ve been feeling about life lately. I find myself whistling to myself while doing chores a lot more now than I ever did in the last couple years.

Speaking of time flying… I was at my parents’ earlier this week; I had a dentist appointment that I had been putting off for some time, and then opted to spend some time in the countryside before I returned to the city. It was a gorgeous, sunny afternoon when I arrived, and I grabbed my camera and headed out to wander about the property for a bit and enjoy it all. In my wandering I spotted the Horse Chestnut above.

My sisters and I planted this tree as a chestnut when I was quite young. I can’t recall exactly how old now, but probably no more than ten or twelve. At the time, my parents took us to music lessons that were held in the basement of a small church. Just outside the church were a couple of beautiful, mature chestnut trees. The three of us loved to stop and browse through the fallen chestnuts, looking for ones whose cases were whole and unblemished, trying to find the perfect, smooth chestnut. We’d usually come home with pockets full of them. I don’t remember what became of most of them – they were likely either used in games we made up, or were lost. But during that period a couple got planted.

Horse Chestnut

This tree is exactly the same age as the first one. We didn’t have any idea of ideal conditions to grow a chestnut tree. In fact, we probably weren’t thinking of the long-term at all, but just planted them as a bit of fun. The first tree grows in an open patch that gets sun through most of the day, the second is in a well-shaded area at the edge of a stand of trees. I don’t know what the rationale behind choosing these two spots was, although the latter was along a path my dad kept mown at the time that we used to play along.

While the first tree grew and flourished in the bright sunlight of its open location, the second remained rather stunted, growing to about a foot high and then seeming to remain at that size for years. It had trouble with rabbits, too, and for a while we had to put a wire cage around it to protect it. I’m not sure what changed; no trees or branches have fallen to open up the sky any more for it. However, it slowly began to grow again.

This week as I arrived for some reason I paused and looked at the tree, growing a short distance from the driveway as it was. And I was somewhat amazed to note that it was now about as tall as I was, with a good canopy of leaves on it. How long had I not been paying attention to it? In my memory it’s still a little sapling two feet high.

Horse Chestnut racemes

Both trees are now somewhere between fifteen and twenty years old. The second has a long way yet to reach maturity. But on the first tree, as I was standing there pondering how quickly life slips by while you’re busy living it, I happened to notice a few white racemes of flowers on a couple of its lower branches. And I thought, what a lovely metaphor for my own stage of life – the two of us, the tree and I, both poised on the edge of maturity. I consider myself a very mature person, but with 30 in sight I feel like I’m reaching maturity – that age at which all those things that one associates with being a “grown-up” actually happen, when people settle into careers, families, homes, and life begins to feel more stable, less uncertain. These are the first flowers the chestnut has produced. I counted seven racemes, nearly all on the lowest, oldest branches.

Horse Chestnut raceme

The Horse Chestnut isn’t a true chestnut at all (which are in the genus Castanea, members of the Beech family), but a member of the genus Aesculus, which also includes the buckeyes of North America. It’s sometimes written horse-chestnut or horsechestnut to avoid confusion with the other group, and to simplify common names of the different species. It’s not native to North America, but is commonly grown as an ornamental, and has since escaped into the wild. You can see why it appeals – the lovely white flower spikes, hinted with pink, are eyecatching in the spring. And what about chestnuts roasting on an open fire? I will admit never to have tried this, however; also, the nuts are slightly poisonous raw, and I presume this is the reason for the roasting.

Children, especially those from the UK, play games with the large seeds – in fact, in some places the tree is known as the Conker Tree, after the children’s game of securing a string to the chestnut and taking turns trying to smash someone else’s with your own (the winning chestnut being the one that doesn’t break). I never played this game, either, though Blackburnian did as a kid. The seeds were also used by militaries in the two World Wars to create acetone, which was then used in the production of armaments. Historically they were also used for whitening and cleaning natural-fibre fabrics, as they’d produce a soap-like liquid when ground and mixed in water.

Horse Chestnut blossoms

Horse Chestnuts are one of my favourite trees, undoubtedly in part for the memories I have of them from my childhood, but also for their interesting leaves, flowers and seeds. I hope someday, when I’m well into my mature years and settled into a home of my own, that I might have a mature Horse Chestnut to shade my home and accompany me through middle age.

April redux

Jumping spider

Towards the end of April I happened across a few observations that I thought would be interesting to post as a wrap-up to earlier topics.

This first one is going back to the jumping spider that I watched pounce at (and miss) a smaller brown spider. The following week I came across the above perched on one of the legs of my tripod. It was huge! Well, relative to my first little guy. It was easily a centimeter and a half long. Black and hairy, with striking orange markings, hard to miss. But the most eye-catching thing about this little spider was its fangs, a radiant metallic green.

The spider belongs to the genus Phidippus, but I’m unsure of the species. The metallic fangs are characteristic of this group, and are used in impressing females in courtship dances. The genus is primarily restricted to North America, and includes some of the larger jumping spider species. Julie Zickefoose apparently has a little black one that keeps her company while working. His name is Boris.

Jumping spider with prey

A bit earlier, I had found this guy hanging out on the wall of the station building. Unlike the individual from my original post, this one had had better luck hunting. He’s munching on a midge, which are extremely common down there.

Worn Compton Tortoiseshell

I came across this butterfly at the end of the morning one day. It was flitting from one tree to another and paused at this birch briefly. I identified it as a Painted Lady, and didn’t really give it much further thought. Then, while preparing the photos for this post I decided I should just double-check that it was a Painted and not an American, because I couldn’t remember which one had the spot on the wing. Well, turned out it was neither. I hunted through the entire Kaufman guide to butterflies twice before realizing that it was an extremely worn, rather orange Compton Tortoiseshell. The first one I’ve ever seen. But now I wonder if I’d been seeing them but writing them off as the more common Ladies.

Worn Compton Tortoiseshell at sapsucker well

It was pausing at the birch trees, and when I looked closer I realized it was drinking sap from fresh sapsucker wells. This species overwinters as an adult and comes out in early spring, much the way Mourning Cloaks do. Because it’s still quite early for nutrition in the form of flower nectar, they take some of their food from other sweet sources, such as sap wells (mentioned in the original post about the Yellow-bellied Sapsucker).

Mourning Cloak at Pussy Willow

And finally, returning to the Pussy Willows. The same day I had the tortoiseshell, I also observed three or four Mourning Cloaks visiting the buds of this Pussy Willow. For the same reason that the tortoiseshell was sipping at the sap wells, these Mourning Cloaks were drinking the nectar available from the female flowers of the willow. I love the velvety red-black of the wings in sunlight. Most butterflies I see that overwinter as adults look a little ratty in the spring. The tortoiseshell had a chunk missing from its wing like a bird had snapped at it. This Mourning Cloak seems to be missing a piece from its hindwing.

April showers bring May flowers

Fancy Daffodil

Fancy Daffodil

I’ve always liked that phrase. A selection of blooms from my mom’s garden. I’m cheating a bit, these were all taken in April. But most of them were the last couple days of April – that’s close enough, isn’t it?

Daffodil
Daffodil

Hellebore
Hellebore

White Trillium
White Trillium

Frilly Daffodil
Frilly Daffodil

Snowdrop
Snowdrop

Red Trillium
Red Trillium

Crocus
Crocus

Tenting it with the family

Eastern Tent Caterpillar eggs

Boy, has this week flown by! Here we are at the weekend already and I feel like the week’s only just begun. Part of this has been the progression of a new project. TheMothMan and I are starting work on a new field guide to the common moths of northeastern North America, which we’re pretty excited about. I haven’t wanted to say anything till I felt it was sure to go ahead, but we just secured an agent to represent the book so it looks like it should be more a question of where, rather than if, it gets published. Our agent also represents such notable naturalists and authors as Julie Zickefoose, David Sibley, Pete Dunne, Lang Elliott…. excuse me while I geek out for a moment. How often does something happen to bring you two degrees of separation from your idols? It’s only slightly less thrilling than if I’d met them in person.

Okay, composing myself… back to the topic at hand. Moths as well, as it turns out. Or rather, their larvae.

The above photo I took a few weeks ago, at the beginning of April. It completely encircled a small branch of a small tree, with white egg surfaces on top, but a crusty golden layer across the bottom. It wasn’t very big, perhaps a couple centimeters at most in its longest direction. I filed it away as “unknown insect egg mass” and there it stayed for a couple weeks. Then, while looking up something completely unrelated (always the way, isn’t it?) I stumbled across a photo in the ID Request section on BugGuide.net that looked just like my egg mass.

Eastern Tent Caterpillar tent

They were Eastern Tent Caterpillar eggs. They were especially conspicuous against the dark bark of the tree they were on, or I may not have noticed them at all.

This week, when I arrived at my parents’ for a couple days, I was struck by the huge number of web tents in the trees. I wondered if there really were an unusual number this year, or if it was just that I was taking more notice this year, what with the motivation of potential blog entries making me more attuned to these sorts of things. Either way, there seemed to be lots of them, two or more in a few trees even.

My mom pulled out her handy dandy Stokes Guide to Observing Insect Lives and we looked it up (my images are nicer… :) ). Over the winter we’d investigated Chokecherry Tentmakers. Thinking that I’d seen several webs in the chokecherry out front, I’d suggested it was these. In fact, they don’t appear till later in the summer. The only web tents found at this time of year are those of the Eastern Tent Caterpillar (Malacosoma americanum).

Eastern Tent Caterpillars

There are two primary species of tent caterpillar: the Eastern and the Forest. The Forest is associated mostly with oaks and maples. The Eastern is found on trees of the Rosaceae family, most notably apple (cultivated, wild, and crabapple) and cherries (cultivated, Black and Chokecherry), as well as hawthorn, pear and plum. Indeed, when I really stopped to look, all the tents at my parents’ appeared to be in the chokecherries, the crabapple, and the cultivated apple trees. And the little tree where I’d found the eggs at the station was also a young apple. When I checked back this week, sure enough, there was a little tent.

Eastern Tent Caterpillar tent

The most obvious sign of their presence, of course, is their web tents. When the caterpillars hatch out of their egg cases they migrate along the branch till they reach a major fork, where they set up shop. This is another feature that tells the tent caterpillar apart from the webworms; tent caterpillar nests are never out at the end of the branches. The young caterpillars all band together in an amazing show of cooperation, building the first little nest to get them started.

As time progresses and the caterpillars eat and grow, they build more layers on the nest to expand it. They lay down silk on the outside of the nest, and as it dries it tightens, eventually separating from the layer it was laid down upon. This creates a stratified effect within the nest. As the caterpillars grow they need more room, but they also require additional layers as the existing ones become filled with frass and moulted skins. The caterpillars leave a hole or two in the webbing, usually near the apex but potentially anywhere, by which they come and go from the nest. You can see the hole here. They tend to lay down the most silk on the side that faces the sun most directly. Usually this is the southern or southeastern side, which allows them to catch the morning rays more efficiently to warm up at the start of the day.

Eastern Tent Caterpillars

You can see in this picture, of a relatively new nest beside my rather dry fingertips, just how small the caterpillars are to start off. They use the nest for a number of purposes. The first and perhaps most obvious is for protection from both predators and the elements. When not feeding, the caterpillars huddle inside the tent. They also use the outside of the tent for basking or huddling to raise their body temperatures prior to heading off to feed, which you can see them doing in this photo. They pack together like this to reduce individual heat loss due to air movement. The stratified layers within the nest also help them thermoregulate, as the silk traps heat like a mini greenhouse. By moving in or out as needed they can adjust their temperature.

Eastern Tent Caterpillars

As the caterpillars move about, they are constantly laying down silk secreted from a spinneret at their tail-end. In going to and from the feeding areas they end up creating silken trails along the branches. They appear to follow these trails when moving, but they’re actually following a trail of pheromones that are also laid down by individuals. Initially, or once a particular source is depleted, individual caterpillars will go on “scouting” trips, looking for good food sources. So that they can find their way back to the nest they leave a scent trail to trace their steps. If they found a really good source of food, on their way back they lay down a stronger, more specific pheromone trail that tells the nestmates where the good stuff is. Well-traveled trails will be strongly defined with silk, while new or lightly-traveled trails may be barely visible.

Eastern Tent Caterpillar hatched eggs

Here you can see the empty egg cases of the little caterpillars, with a silken trail leading away towards the nest. The eggs are laid by the adult moths in the late spring or early summer, about 200-300 in a single egg mass. It doesn’t take long for the caterpillars to develop within the eggs, only about three weeks. However, they then remain dormant until the following spring. They hatch out just as the leaves are beginning to unfurl. Occasionally, the caterpillars from two or more egg masses laid close by to each other will come together to form a single colony. I think that’s what happened in the case of this bunch, since I found at least three empty egg masses within the same branching system, but only one nest.

Eastern Tent Caterpillars

The caterpillars will eat and grow and shed their skins and eat and grow some more for 4-6 weeks. They’ll go through six larval stages, or “instars”, each one still a caterpillar, but getting progressively larger. In their sixth instar they stop laying silk down on the nest or trails, instead conserving it for pupating. It’s during this stage that you usually find the caterpillars on sidewalks, benches, roads, and elsewhere, as they disperse from the nest to find a safe location to spin their cocoon and pupate. The cocoon is usually tucked into a corner or crevice, and is fuzzy and imbued with a yellow powder.

Eastern Tent Caterpillars

The caterpillars come out of their nests three times a day to feed, all corresponding with the times of lowest predator (especially bird) activity: at the crack of dawn, in early afternoon, and at dusk. The only deviation to this pattern is in their final stage, when they only emerge at dusk. They back this up with a chemical deterrent. Apple and cherry tree leaves, in particular, contain small amounts of cyanides, which the caterpillars ingest. When disturbed they produce cyanide-laden fluids to dissuade predators.

Eastern Tent Caterpillars

Tent caterpillars are much-maligned because they’re a defoliator. I recall as a kid being under the impression that tent caterpillar nests, when found, should be cut from the tree and burned to prevent spread of the infestation. What a dramatic reaction! An individual nest will not do significant harm, and in fact even an outbreak of the insects will not do any lasting damage to a tree. The caterpillars rarely kill their host trees, usually only if the tree was already weak or damaged prior to infestation. Any defoliation caused by the insects will generally regenerate later in the summer, once the caterpillars have headed off to pupate. Of course, depending on the size of the colony, it may be possible that that year the tree doesn’t produce any fruit. I think this may be where their bad rap stems from – they would be nuisance pests in orchards where they may stunt the fruit crop for the year. They are likely also perceived as unsightly in suburban settings (both their nests and the resulting defoliation). But really, they’re pretty harmless.

The only potential problem the caterpillars may cause is they’ve been implicated in Mare Reproductive Loss Syndrome (basically abortion by horses). The going theory is that the hairs of accidentally ingested caterpillars may puncture the intestinal walls and provide a conduit that allows bacteria to enter the uterus.

Eastern Tent Caterpillars

I like to cheer for the underdog (unless there are obvious good/evil sides), and so I support the tent caterpillars, much as I back Purple Loosestrife and Brown-headed Cowbirds (subjects of future posts, I’m sure). They’re a good food source for many creatures, including as many as 60 species of birds, maturing just when the birds are looking for bugs to take home to feed the kids.