Monarch chrysalis

Empty Monarch chrysalis

November seems to be the time of leftovers and left-behinds, as animals head south, or into hibernation, or otherwise start preparing for winter. November is when I start seeing the summer’s empty birds’ nests, old cocoons, empty shells of things. It’s probably in part because with the animal and plant life disappearing, the eye is drawn more to the inanimate.

I spend a lot of time staring at the ground in November, and so I was doing when I came across this. It was just a bit of curled up paper hidden in the grass, and I nearly dismissed it as a bit of birch bark before pausing for a better look. Stooping down, the bit of paper revealed itself to be an old, long-since-vacated chrysalis. Naturally, I’d left my camera back at the house on this particular outing, so I decided to break off the grass stems and bring it back.

Caterpillar silk is surprisingly strong. I broke off the two grass stems that the chrysalis was obviously attached to, and lifted gently, but there was still another. So I snipped that dead leaf and tugged again, and it was still affixed to something. I broke five bits of grass to finally be able to get it out, and a sixth was hanging by a thread of silk, which I sawed through with a fingernail. No surprise this stuff makes good clothing.

The light was waning when I got back to the house, but I ran off a series of shots. Even though the sides of the chrysalis are in tatters, enough of it remains intact that it’s easy to see the identity of its former occupant: The roundish top, the beaded ring a third of the way down (now lined with black), and the general size all clearly mark this as a Monarch chrysalis. While it housed a metamorphosing caterpillar, it would have been minty green, and that ring of beads was gold.

Empty Monarch chrysalis

When I started taking photos, I was surprised by the pattern of black on the top, where it attached to the grass. The stem itself is called a cremaster, and is formed from the tail-end of the caterpillar just before it sheds its skin for the last time. The caterpillar makes a silk “button” then shoves this black rod into it in order to affix itself; once done, it hangs from its tail, curls into a J, and splits its skin along its back. For an amazing sequence of photos, strung into a video, of a Monarch caterpillar changing from caterpillar to chrysalis, you should check out this NPR page, a commentary by Julie Zickefoose. Julie’s also got some amazing transformation photographs at her own blog – here, here and here, for instance. Every year she brings in a couple of fifth-instar caterpillars so her family can watch them metamorphose from larvae to butterflies.

Empty Monarch chrysalis

The outside of a chrysalis or pupa is effectively the sixth skin of the caterpillar (it’s already shed five, to get here), rather than an external structure such as the hairy cocoons moth caterpillars make. Because of this, many of the structures of the winged-adult-to-be are defined in its hard shell. With moth pupae, especially, it’s possible to see the shape of the wings and antennae of the adult moth. Butterfly chrysalids need to be more camouflaged and tend to show other shapes (or at least, I presume that’s the reason they show other shapes; they don’t have the same hairy cover that above-ground-pupating moths make).

But I did notice something else on this one: the spiracles that line the abdomen of the insect. Spiracles are the insect’s “nostrils”, the holes through which it breathes. All insects have them, but on many (most?) they’re well-hidden. I thought it was interesting that they were so prominently visible on this old shell; you can see them on the green chrysalis, too, but not as clearly.

And then the other interesting thing I discovered, while poking about BugGuide.net, was mentioned on this photo and this photo… Apparently you can sex the insect inside the chrysalis based on the presence or absence of a small line at the base of the string of black dots. I’ve indicated it in this photo using a yellow arrow. If the line is present, the insect is a female; if it’s absent, the butterfly is male.

This is the first Monarch chrysalis I’ve ever seen in the wild. It would have been more exciting if it had actually contained a Monarch at the time that I found it, but I still think it’s pretty cool!

Monarchs

monarchs mating

A couple of days ago I’d stepped out into the front yard to hang out a few items to dry, and as I was standing there I was passed by a large, fluttering shape. It took me a few moments to register what it was. It fluttered rather like a butterfly, but the creature seemed to be carrying something. When it came round and passed by me again I realized that it was, in fact, a butterfly, and it was indeed carrying something. It was a pair of Monarchs, locked in copulation. The male was fluttering about while the female dangled below him, her wings folded as he flew so as not to interfere. I watched them for a bit, and after a couple of loops around the yard they finally settled low on the spruce tree, and I dashed for my camera.

I have noticed several Monarchs already this summer, though this is the first mating pair I’ve seen. I’ve been delighted by their abundance. Our fields here around the house are stuffed with milkweed, the greatest density of the plant that I’ve seen anywhere. On a warm summer evening, with a light breeze blowing through the flowers, the deliciously sweet scent is almost heady. Last summer, when we’d first moved in, I’d regarded those fields with great anticipation of the abundance of Monarch butterflies that we would have, and, especially, Monarch caterpillars, which I had never seen. If I was exceptionally lucky, perhaps we’d even find a chrysalis. But all last summer I saw only two or three individuals. I found only a single caterpillar.

Common Milkweed, Asclepias syriaca

The fact that I’ve seen better numbers this year is encouraging to me, especially since reports out of the south after this winter suggested that the Monarch population really took a hit this year due to severe weather and threats from deforestation, and might even be at the lowest levels in over three decades, with the overwintering masses filling only a quarter of their usual acreage. And as if that weren’t enough of a challenge, increases in recent years in the use of herbicides in agriculture here in North America, eliminating milkweed from fields and reducing the amount of hostplant available to monarchs, might also have an effect on populations.

I am sure that over the long history that Monarchs have been wintering in these restricted areas of Mexico this isn’t the first year that they’ve been affected by storms and other weather phenomena that have hammered populations. The difference is that ordinarily they could bounce quickly back because that was the only challenge that faced them. Now they’ve got habitat loss through development and herbicides with which to contend, and whether they recover or not is as much up to us as it is to nature herself.

They have a safe haven here, at least, a veritable milkweed paradise.

There and back again

Monarch

Yesterday morning I did the bird census down our road. It was a lovely morning, cool, but not unpleasantly so, clear and sunny. As the sun rose, it warmed up, so by the time I got down to the meadows at the end of the census route, it was feeling pretty comfortable. Perfect weather for migration. It wasn’t just the birds who were on the move, though – so were the monarchs. I haven’t seen very many monarchs since arriving here, just the odd one here and there. Yesterday morning I probably saw about a dozen during the census – enough for me to note their increased abundance.

In northern climates, where the environment cools down or freezes during the winter, animals have evolved various ways of coping. For insects, most of which are unable to be active when it’s very cold, there are two strategies, stay or leave – overwinter (essentially a hibernation of sorts) or migrate. Monarch butterflies fall into the latter category. Monarchs are long-distance migrants, and the individuals I saw in the meadow yesterday will, in a few months, be spending a nice balmy winter in central Mexico.

Monarch

There are three distinct populations of monarch butterflies – one east of the Rocky Mountains, one west, and one in Central America, all of which have unique migration patterns and overwintering destinations. About 90% of Canada’s monarch population live east of the Rockies, and all of them will head down to one of perhaps a dozen spots in central Mexico to spend the winter. These sites are all high-elevation oyamel fir forests located within about 800 square kilometers (309 square miles). This area has been designated as the Mariposa Monarca Biosphere Reserve.

Monarch

The population from west of the Rockies winters further north, in central and southern California. There are about 200 known overwintering sites in the state, with anywhere from dozens to tens of thousands of individuals present at each site. The Central American population doesn’t undertake a latitudinal migration, but mostly moves short distances of 10 to 100 km (6 to 60 miles) from highland to lowland areas.

Not surprisingly, with populations overwintering in such concentrations, both habitat loss and natural disaster pose serious potential threats. I would be extremely surprised if the population hadn’t gone through such events before, and obviously had survived and rebounded, but it does pose some concern, especially in the face of climate change that has the potential to produce more numerous and more severe storms and conditions than the butterflies are used to weathering.

Monarch

A monarch butterfly hatched at the beginning of the summer may only live for two months, but those hatched at the end, the ones that undertake migration, will enter a non-reproductive state that allows them to live for up to 9 months, enough to get them through the winter and started back north to breed again. Of course, it’s not enough to get our Canadian butterflies back home to us, so those monarchs that I saw in the meadow will not return. Rather, monarchs have developed a strategy to circumvent this short lifespan and still allow them to migrate. The butterflies that overwintered in Mexico will move north to breeding sites in the southern US in March and April. There they lay eggs and go through two or three generations. The latter generations are the ones who continue the push north, as the original adults by that time have died. This step-by-step generational approach to migration allows the monarchs not only to take advantage of milkweed as it starts growing in each region, but also helps to build up the population, which suffered losses over the winter. As well, by going further north, the species can produce up to three additional broods beyond when milkweed begins to die off in the southern US in June.

Our Canadian monarchs finally make it home in late May or early June. Those west of the Rockies may not return to British Columbia in all years. The best years are warm, dry summers, or summers with extended periods of sunny weather. The mechanisms by which the later generations find their way back north again is still unclear, but there is obviously a genetic component to it.

Monarch

During southbound migration, monarchs prefer to stick to dry land and are reluctant to cross large bodies of open water (such as the Great Lakes). Part of this is because of their migration method – they use air thermals, rising columns of warm air heated by the sun striking the earth, to gain altitude, where wind currents higher in the sky will help give them a tailwind, or where they can glide down to the base of the next thermal (much like hawks). These thermals can sometimes take the butterfly to incredible heights – sometimes up to a kilometer (0.6 mile) high.

Monarchs at migrant trap

Air thermals don’t form over open water, so it’s much more work for the butterfly to cross a large lake than it is for them to follow a shoreline. However, sometimes following a shoreline leads them into what are often called migrant traps – places where the geography of the land naturally causes migrants to accumulate (this applies to both birds and butterflies). Because going in reverse counters their natural instincts, the migrants remain at the trap until such time as favourable weather occurs for crossing over the lake. Sometimes this is simply the next day for butterflies, if they’ve arrived mid-day, or sometimes they may hang around for a few days, if a string of cold or wet days occur.

One such migrant trap is the Leslie Street Spit (Tommy Thompson Park) on the Toronto waterfront. Although I was away most years, I was fortunate to be able to experience the migration last fall. Often monarchs will make a significant push on just one or a few days, leading to huge concentrations (for here, anyway; they’re paltry compared to those on the wintering grounds). We lucked out in catching the one big one last fall – we’d noted increased numbers of monarchs passing through earlier in the morning, and later in the day a trip to the tip of the spit revealed clusters of butterflies clinging to the tree branches, waiting for the next day to cross the lake.

Monarchs at migrant trap

We estimated there were perhaps 15,000 to 17,000 butterflies out there, split up over three or four locations, but with at least two thirds of them in a single large woodlot at the end. It was an amazing sight, but interestingly, a surprisingly cryptic one. When we first approached the woodlot we weren’t sure there were many butterflies there. It wasn’t until we actually walked inside amongst the trees, and disturbed a cluster, that we began to notice them. Then, once we started really looking, they were everywhere. Walking through from one end of the woodlot to the other was magical; as you passed the butterflies would rise from the branches where they were hanging and filled the air in golden clouds, before settling back down again once you’d passed. So light on their wings, it gave the space a more airy feeling than if it had simply been empty.

Monarchs at migrant trap

I probably won’t see numbers like that again without a special trip down to Lake Ontario; although monarchs will still roost together in smaller groups, such migrant traps just don’t exist away from the lakeshore. But even still, watching the butterflies dance among the meadow flowers is also very captivating and peaceful.

You can join in and help track monarch migration with the citizen science program Journey North, which invites you to submit your monarch observations to be included in a map compilation. The site also has lots of other great info about monarchs and monarch migration, including maps of this year’s migration.