Potluck

a selection of summer delicacies

You never know what might be offered at a potluck supper, where you browse over a miscellaneous collection of dishes. This essay is a bit like that—an assortment of unrelated but potentially interesting observations and information.

Last week I mentioned the great abundance of mosquitoes in June in the Interior. Mosquitoes can surely be a major nuisance and in some regions of the world they carry diseases and parasites. But is there another side to this coin?? What good are mosquitoes?

Mosquitos are good bird food. Swallows and swifts catch them on the wing. Certain warblers and flycatchers dart out from a perch to catch them as they fly by. I’d bet that the female hummingbird swooping back and forth in my front yard catches some, too. Mosquito larvae are aquatic and provide good prey for small fish and for larger invertebrates that are also prey for fish. Dragonflies and damselflies feast on them.

Mosquitoes are more than unwilling prey, however; they are the principal pollinators of a diminutive-flowered plant called the small bog orchid. In Alaska, males and females of several species of mosquito are known to visit these orchid flowers and carry pollen from on flower to another (other insect visitors include small moths and flies, but their role in pollination is undocumented). As the mosquitoes poke into a flower, globs of pollen are slapped onto their eyes, where they stick until the mosquito goes to another flower, which is arranged in a way to pull off the pollen, leading to seed development. There may well be other kinds of small flowers that are pollinated by mosquitoes: male mosquitoes commonly live on nectar from flowers and even the blood-sucking females do to in some cases. Some of these visitations might achieve pollen transfer, but sometimes the mosquito might be just a nectar thief.

Flower color is one of the cues used by flower-visiting animals. Color helps identify the species, sometimes the age of the flower, and in some cases, whether or not it has already been visited by a pollinator. Usually, all the flowers of a particular species are the same color, or nearly so. But we see exceptions. For example, almost all of the chocolate lilies we see have brownish flowers, but very rarely we see one with yellowish flowers. Wild lupines normally have blue to purple flowers, but in rare cases we find one with pink flowers. Occasionally, we’ve found white-flowered individuals of fireweed, northern geranium, shooting star, and bluebells (whose flowers are normally pink or blue). These very unusual flower colors are presumably the result of genetic mutations.

yellow-chocolate-lilies-Denise.jpg
Photo by Denise Carroll

These mutants don’t seem to spread and become more common in their respective populations. But why? Do pollinators discriminate against those oddballs, leaving them unvisited, unpollinated, and without offspring? Or, maybe the (presumed) gene that controls flower color also controls something else in the plant’s life, something that interferes with some aspect of normal function. Multiple effects of single genes are common. As usual, a simple observation leads to more questions.

Bumble bees are very important pollinators of many kinds of flowers. They are the principal pollinators of monkshood, lupine, blueberries, iris, louseworts, and beach pea, which have flowers that must be manipulated in a certain way in order to achieve pollination. But the bees also join with a variety of other critters to pollinate roses, salmonberry, thimbleberry, goldenrod, and columbine (to mention just a few).

However, all across North America, from California to the east coast, populations of some bumblebee species have become very rare or even disappeared entirely. Because I have a very unscientific impression that I see fewer bumblebees on our wildflowers in the last two years than previously, I wondered if our bees may also have crashed. I asked the UAF expert, who said that a study currently underway in Denali is designed to detect major changes in bumblebee populations there, but as so often happens, these seem to be no scientific data for Southeast. We can hope that our bumblebees are in good shape, because so many of our wildflowers depend on them.

Finally, and just for fun (?dessert at a potluck?): One day I walked through the Eagle Beach day-use area after a stroll on the beach. I spotted a big black bird sitting on a rock and holding a chunk of something red and drippy in its bill. Through binoculars, I saw that the raven held a succulent piece of watermelon. Just beyond the rock was a picnic table with several plastic containers, temporarily abandoned by a human family that was playing out on the intertidal sand flats. At least two of those containers had the lids removed (?by the raven?) and one of them still held a chunk of melon. That family was in for a surprise when they came back to their table!

Roadside natural history

buzzing bumblebees and rototilling ravens

Cruise around Juneau on most any day, and chances are good that you’ll see something interesting or beautiful or both—things you can enjoy without driving into the ditch!). For instance, as pleasant relief from our customary shades of green and gray, there are the blue lupines and forget-me-nots and the creamy elderberry flowers.

At the end of May this year (a late, late spring), the shooting stars were finally coming into gorgeous bloom in the meadows between Freddie’s and the Lemon Creek junction. Look for swathes of pink flowers amid all the burgeoning greenery. And perhaps consider that these flowers, with their reflexed petals and all the reproductive parts hanging out in front, are pollinated by bumblebees. The bees land on the flower and buzz, so the pollen is shaken out onto the bees. Although the bees take some of the pollen home to feed their offspring, some of the pollen is transferred to the next shooting stars that the bees visit, and those flowers can then set seed.

You might see a gang of ravens rototilling a patch of mown grass. They dig up the old grass and the soil surface, leaving tufts of dry grass all around. There must be some kind of grub or worm that attracts all this attention. I’ve seen similar activity in other places, sometimes by crows. Robins too will rototill patches of moss. I’d love to know what they’re searching for!

rototilling-ravens-cropped-for-paper-David
Photo by David Bergeson

We often see deer and porcupines grazing along our roads, and sometimes flocks of siskins or crossbills come down to get grit or salt. But it’s bears that generate the most excitement from folks that are passing by. We can see roadside bears in several places, but possibly the most common area for bear-spotting is the ‘new’ Auke Bay by-pass.

Bears often come to forage on greens, such as dandelions, that grow alongside the roads, and they are fun to watch and photograph. However, there are two unfortunate side effects of this attraction. One is tha numerous cars may line up at the edge of the road, creating what is known as a ‘bear jam.’ This becomes a traffic hazard, with open car doors and people walking around, paying more attention to bears than to traffic.

The second unfortunate side effect is that over-eager photographers often crowd the bears, which can make the animals nervous. A nervous bear is unpredictable and may try to swat or charge a person that comes too close, perhaps leading to human injury. Injury to a human—even when the human brought the injury upon itself—sometimes results in (unfair) lethal action against the bear. Or possibly a nervous and annoyed bear might suddenly bolt across the highway, maybe with cubs in tow, and become a traffic casualty. Obviously, the bottom line is “Give the bears their space!”

Even whales can be seen from some of the highway pullouts (there are not many places in the world where you can do that!). When you see a humpback whale, consider that it feeds on small fish such are herring, which feed on krill and copepods (small invertebrates, which eat plankton)—and the phytoplankton (microscopic floating algae) get much of their nutrition from nutrients washed down in the streams from the forest, rocky peaks, and glaciers. In a sense, the rich foraging for whales that come here mostly in summer is provided, partially but ultimately, from the forests, muskegs, and glaciers.

Some roadside places offer good spots for watching ducks and gulls and maybe American dippers, as they forage and loaf around. Sheep Creek delta is one such place, for example, with pullouts right near the bridge.

Insects in August

nesting bees and willow galls

An observant friend was hiking up Mt Juneau one day in mid August. He was apparently the only one of the hiking group to notice a bumblebee that was digging a hole in the dirt at the side of the trail. A little farther along, he spotted another one, doing the same thing. I am envious, because this is something I’ve never seen here.

These bumblebees are queen bees that will hibernate in such holes over the winter. It seemed early to be thinking of hibernating, but perhaps our cold summer is sending them to bed before fall really arrives. Or perhaps they need to scout around for a while to find a suitable site. The queens have already been fertilized by the males, and these newly-fertilized queens are the only ones to live to next year: the males, the worker bees, and their queen-mother all die.

bumblebee-digging-nest
Bee digging nest

Next spring, the queens will emerge and forage on flower nectar and pollen. Each one will build a small nest of plant fibers and lay a few eggs, usually less than ten or so. Sometimes the mothers-to-be take over old mouse nests for rearing their broods. The queens provision the nest with pollen, on which the larvae feed. After roughly three weeks, the larvae become worker bees (sterile females). The queen makes several broods during the summer, each batch of short-lived workers helping to feed the next brood. Bumblebees live in much smaller colonies than honeybees; most nests are only two or three inches in diameter.

Both kinds of bees, however, are seriously declining, apparently because of virulent pathogens to which they have little resistance. The decline of the bee populations becomes a serious problem for humans, because so many of our fruits and vegetables are pollinated by bumblebees and honeybees. Think tomatoes and squashes, peas and beans; think apples and cherries, blueberries and blackberries and strawberries…the full list is very long indeed. If a solution to bee declines is not found, our diets will be much impoverished.

Out near the glacier, watchful rangers noticed a bear, which had just feasted on sockeye salmon, nipping off certain willow leaves. Each of the selected leaves had at least one and sometimes six or eight spherical lumps near the midrib. A few of the lumps were reddish on top, but most were pale green. Each one was about the size of the end of my finger.

These round lumps are galls, produced when an insect lays eggs on the plant. The insect’s activity, and that of the developing larva, manipulates the plant’s hormones in a way that induces the plant to divert some energy and materials to making the gall.

The galls are hollow, each inhabited by an insect larva that feeds on plant tissue inside the protective sphere. Dissection of a few galls by a helpful researcher at the Forestry Sciences Lab showed that the larvae are Hymenoptera—the order that includes bees and wasps. A little further research identified the gall as belonging to a kind of sawfly that specializes on willows. They are called sawflies because each female has a long ovipositor (egg-placer) with which she saws a hole in plant tissue to house the egg.

From the larva’s perspective, the gall provides not only a degree of protection from many (but not all) enemies, but also nutrition. The lining of the gall contains lower concentrations of several defensive chemicals than the outer part of the gall or the rest of the leaf.

From the willow’s perspective, the gall does relatively little harm to the plant. But male willows may be attacked more heavily than females by the galling insect—in at least one willow species, males provide more nutrients because they have more nitrogen, phosphorus, and potassium in the leaves than females. In some cases, the gallers prefer to use willows that grow most vigorously and have the longest shoots.

What might the bear be getting from its selective foraging? No one knows!

Outdoor therapy

natural remedies for a downhearted mood

One day recently, I was feeling quite grumpy, disgusted, annoyed, and getting down-hearted, so I decided to cheer myself up by thinking about ‘a few of my favorite things’ that happened in the past couple of weeks.

On Hearthside’s annual author’s cruise, a humpback whale put on a fabulous show. She swam along a shore, pec-slapping vigorously, and then turned around and did the same coming back—sometimes flailing both pectoral fins at once. Then we saw that she had a calf alongside, and the two of them breached repeatedly. They were attended by several sea lions, who jumped and cavorted in and out of the waves created by the breaching. The show had everyone on board in a state of happy fascination.

A trip up Gold Ridge above the tram was a good one, despite the heat that had me just creeping along. The marmots were, sensibly, dozing in their cool burrows (unlike Alice falling down a rabbit hole, I did not fit the burrow entrances—too many cookies, perhaps?). Bumblebees were busy, attending to the tiny blossoms of alpine blueberry growing close to the ground in a tight mat. The alpine zone was a sea of flowers (I counted over twenty kinds, including one that was a complete mystery to me). An American pipit perched on a hot rock, overseeing his nesting territory of alpine tundra and rocky outcrops. Two male rock ptarmigan showed off their brilliant white plumage in soaring flight displays from one rocky tower to another, cackling all the way—still looking for ready females. As the afternoon breezes picked up, ravens began to play in the air currents, sharing air space with hang gliders.

One day I sauntered around some muskegs with a friend, just seeing what we could see (a most enjoyable occupation!). Even though the ponds were mostly dried up, a few held some stubborn water striders, and the mud held evidence of the passage of jays, squirrels, mice, and other small beasts. We noticed a fly bearing an irregular yellow patch on its back, perhaps pollen from a floral visit. It found another fly, which obligingly spread its wings and allowed the first fly—now clearly a male—access to her rear end. They copulated for several minutes; through his beautiful, translucent blue abdomen, we could see his internal organs moving. Together they moved around in the low vegetation; eventually she brushed him off under a twig.

The beavers seem to have returned to Steep Creek, after an absence of several years. We had seen beavers visiting the lower ponds, but this time it looks more serious. The broken dams have been rebuilt and a friend watched a beaver collect a huge mouthful of grass and carry it toward the old lodge. This made me wonder if the grass might be bedding for a young family. There is hope, then, that the beavers may restore the upper dams as well, creating ponds that trap sediment, provide fine rearing habitat for juvenile coho and Dolly Varden, and good foraging habitat for birds. In the past, the sockeye and coho salmon that spawn in this stream proved themselves quite able to surmount the previous dams, and there were good populations of both species in the creek.

The rains came! Not, this time, a source of gloom but of gladness! May was a drought month in Juneau, with very high temperatures on several days. Muskeg ponds dried up, lichens and mosses got crispy, and streams turned into trickles. But the soft rains in early June brought lower temperatures and turned Juneau into its usual lush, verdant self; the creeks flowed again. (And now we are ready for some more sun!)

There, that’s a list of good things observed. Thinking about all that, I found that I was still grumpy, disgusted, and annoyed—oh yes—but it no longer got me down-hearted. Good stuff!—simple things for a simple mind, maybe, but equanimity was restored!

Monkshood flowers

specialties and cheating bees

One warm but very windy day, a friend and I were perched on top of Gold Ridge in a small swale that provided some shelter from the wind. The alpine meadow was dotted with the purple flowers of monkshood. I had forgotten the structure of monkshood flowers, so I spent a few minutes opening one and examining the arrangement of parts inside.

The structure is really quite odd—very different from most other flowers in our area—although there are dozens of other species of monkshood (genus Aconitum) elsewhere in the world, which suggests that this odd structure is one that works well. Monkshood flowers are considered to be pollinated chiefly by bumblebees, although other animals may also visit the flowers occasionally. As I examined my specimen flower, it occurred to me that perhaps it would be interesting to learn how bumblebees visit and exploit the nectar while (potentially) depositing or exporting pollen.

Monkshood flowers are slightly complex, requiring a visiting bee to enter and move in a particular way. Most bumblebee species are generalists, capable of exploiting several kinds of flower. Naïve, inexperienced bees have no trouble figuring out simple, open flowers such as those of buttercups or roses, but they have to learn how to exploit more complicated flowers such as lupine or monkshood, and it may take a number of tries before the bee succeeds in getting to the nectar—indeed, these failed foragers often just give up. One species of bumblebee is considered to be a specialist on monkshood (elsewhere) and this species has a very short learning period, quickly getting to the nectar.

To explain what a bee has to do in a monkshood flower, I first need to describe a typical monkshood flower so an interested reader can then visualize a bee’s activity. In most other flowers, there are colorful petals that are backed by protective green sepals, but in monkshood, the purple exterior of the flower is composed of sepals that have been transformed to function like petals. There are two small sepals at the lower edge of the flower and two large, lateral sepals. Most conspicuously, there is a large, expanded sepal that forms a hood on the top of the flower (botanists perversely call this a ‘helmet’). The hood is reminiscent of the cowl of a medieval monk—hence the common name.

bumblebee-and-monkshood-by-bob-armstrong-2
Photo by Bob Armstrong

Inside the flower, at the base of the sepals, lie the working parts: lots of short stamens offering pollen in their anthers, to be picked up and exported by a flower visitor (male function) surrounding a few stubby pistils that will become fruits if pollen is deposited on their receptive stigmas (female function). Inside the expanded hood lie two true, narrow petals that bear nectaries tucked way up into the top of the hood. To get to the nectar, a bumblebee has to reach or crawl inside the flower, passing over the sexual parts as it does so, picking up or depositing pollen.

As is so often the case, our local species of Aconitum (A. delphiniifolium) has not been studied, so research on other monkshood species may be used to shed light on the local species.

Japanese researchers experimented with the flowers of their monkshood species: they removed one or more sepals and watched the behavior of bumbles on the manipulated flowers, recording the amount of pollen picked up and deposited by the visiting bees. Removal of the large lateral sepals deprived a bee of her usual platform for standing in the flower while she reached up to the nectaries. This meant that her body did not contact the anthers or stigma properly, so pollen pick-up and deposition (and fruit set) was reduced. Removal of the small lower sepals had little effect except that a bee had some trouble entering the flower. Taking off the hood of the flower changed the look of the flower greatly, but bees still visited. However, sometimes the bee extended her tongue into the air instead of inserting it into the nectary, so although the pollination effectiveness of the visit was adequate, the bee often got no reward—and that would mean that the rewardless bees would be less likely to visit other such flowers. The researchers suggest that the function of the hood is to guide a bee’s tongue to the nectaries and perhaps also to maintain the concentration of sugars therein, thus keeping the bees’ interest in visiting.

In at least some species of monkshood, there is considerable variation among populations in the depth of the nectary and hence in the distance a bee has to reach in order to get nectar. A long nectary can only be reached by a long-tongued bumblebee species; short-tongued bumblebees have trouble reaching the nectar in the normal way and may become nectar-robbers, by chewing a hole in the hood and reaching into the nectary that way. Nectar robbing may reduce visits by good pollinators and has the potential to reduce both pollen export and deposition.

Bumblebees

be kind to them!

In early spring, I look forward to seeing the first bumblebees, visiting willow catkins and early blueberry flowers. These ae queens, which mated last fall and then hibernated, each one usually in a small chamber she dug in the soil. Bumblebees can regulate their own body temperature by shivering (as can dragonflies and hawkmoths), and so they are able to be active when many other insects are immobilized by cool temperatures.

The springtime queens find sites for their nests, often using abandoned mouse or vole nests. They need the insulation provided by the fur, dry grass, moss, and feathers that the rodents gathered, but they may also drag in additional material from nearby. In each nest, a queen builds a wad of pollen on which the eggs are laid and the larvae will feed; she also builds a tiny nectar pot where she stores nectar for herself. The queen incubates her brood and feeds the larvae on regurgitated pollen and nectar. Total development time from egg to adult bee takes four to five weeks. The first brood of the season is typically small, fewer than twenty eggs; later ones may be larger, because there are then worker bees to help raise them.

bumblebee-digging-nest
Digging a nest. Photo by David Bergeson

Newly emerged adults are mostly workers; some stay in the nest to help tend the next brood and other become foragers, gathering nectar and pollen to feed the growing colony. Different kinds of flowers provide different quality (and quantity) of nectar and pollen: some nectars are rich in sugars and may differ in the specific sugars provided. Pollens also differ among flower species, with some (for example, legumes such as lupine and beach pea) having higher protein and different amino acid composition than others (such as roses and blueberries).

Foraging bumblebees can be quite selective in their choice of flowers, and the more well-stocked the nest larder, the more selective they become. They learn to use visual cues such as color and shape, and respond to the level of food reward (nectar or pollen) offered by the flower: flowers that offer high rewards are visited more often. And they learn how to handle different kinds of flowers, some of which hid the nectar or pollen deep inside a complex structure (think of lupine or monkshood) that requires a bee to manipulate the flower in a certain way to gives access to the food reward and achieves deposition of pollen and transport of pollen to another flower.

Foragers also learn to use scent cues, provided by the flower and by other bees. Foraging bees can leave scent marks on flowers they’ve visited, cuing other workers to avoid the depleted flower. When successful foragers return to their nest, they can signal their success to other workers. The returning forager runs around the nest excitedly and releases particular scents that stimulate other workers to search for the floral scent carried by returning bee. Unlike the more famous honeybees, however, bumblebees don’t signal the direction in which the food source was found.

Later in the summer, queens (and in some cases, workers too) begin to lay unfertilized eggs, which develop into males. The males do little around the house, so to speak, but sally forth to feed and look for mates. Males of many species establish a scent-marked route through their habitat, leaving their scent marks on selected sites such as rocks or tree trunks; they then patrol the route in hopes of attracting females. Other species set up small territories and perch there, defending their chosen spot from other males and waiting to accost a passing female. The females of interest are newly emerged queens; when mating is successful, the new queens go on to find hibernation sites in which to await the coming of spring. The workers die off and our new queen bumblebees may have gone to bed by now.

Many hazards threaten bumblebee colonies. Domestic colonies of bumblebees spread disease to wild populations. There are predators and parasites, of course, and environmental hazards such as flood, habitat destruction by humans, pesticides, and so on. In addition, occasionally the balance of power between a queen and her workers shifts, and the workers kill their mother; they may then rear their own sons (from unfertilized eggs). Sometimes a late-emerging queen who fails to find a good nest site turns assassin, invading a recently established nest of the same (or closely related) species, killing the resident queen if possible, after an intense battle, and usurping the brood of workers to rear her own offspring.

There is a distinctive type of bumblebee called the cuckoo bees. They are tougher and have more powerful stings than regular bumblebees. They make their living by invading young colonies, killing the queen, and usurping the old queen’s position in charge of the colony. The invader may kill and eat the host’s eggs and larvae; any surviving workers rear the invader’s offspring, all of which will be males or future queens of the invader’s species (the host nest seldom produces queens after it has been invaded by cuckoos).

Here in Southeast, a recent publication indicates that we may have about seven species of bumblebee (of over forty in North America), including one species of cuckoo bee. They are essentially impossible for non-experts to identify without killing the specimen. The easily visible banding patterns of yellow and black and sometimes red are remarkably variable over the range of a species and can vary even within more limited areas.

Difficult to identify but fun to watch: what flowers are being visited, how does the bee handle the flower, how long does each visit last, does a given bee visit more than one kind of flower and if so, where on the bee is the pollen deposited. The questions are many.

A cautionary note: Be nice to our bumblebees! Many populations of bumblebees are declining, rapidly in some areas. But we need them to pollinate our flowers! Without good pollination, there would be poor fruit crops, hungry bears and birds, much less jam and pie– a very sorry state of affairs!

Lupine puzzles

banner petals and a naming mystery

Lupine plants are common around here, and perhaps you’ve noticed that the uppermost petal (the so-called banner petal) is sometimes white and sometimes dark pink or almost purple, while the side petals are typically blue. If you look at the whole inflorescence, you quickly notice that the newer, white banners are on the upper flowers, whereas older, pink or purple banners are on the lower flowers. There’s a story about why the upper banners are white and the lower ones are pink or purple.

Many kinds of flowers exhibit color changes, and studies of several species have shown that the color change serves as a signal to visiting insects, directing them to the most rewarding flowers. For example, in certain species of Lantana, the young flowers in a cluster are yellow but turn red as they age. Clusters that retain the old, red flowers are more attractive from a distance than those without the red flowers, but close up, pollinating insects clearly discriminate between yellow and red flowers, favoring the yellow ones that still have nectar.

lupine-by-bob-armstrong
Photo by Bob Armstrong

Similar reports can be found for lupines, in which the color of banner petal changes. In the case of our local lupines, the story is that the white-bannered flowers have not yet been visited by pollinating bees (or perhaps were visited only very recently and there has not been time to make the color change), whereas those with darker banners have already been visited, and potentially pollinated, and were no longer worth visiting. One local observer has noted that bees do seem to favor the white-bannered flowers. Nice story!

But then, one day I noticed that bumblebees were regularly visiting the flowers with dark pink banners. So either the bees were really naïve, perhaps recently emerged workers with no experience, and had not yet learned to read the signals (a real possibility, but how could I tell!) or else those older, darker flowers still had something to offer to a bee.

I decided to look more closely. I collected a sample of young, white-bannered flowers and another sample of darker, older flowers, and dissected them. As expected, the white-bannered flowers seldom had pollen deposited on the female parts and there was lots of pollen still in the pollen sacs. However, the darker-bannered flowers did not conform to the story’s expectations. Indeed, the female parts of the darker flowers sometimes bore a wad of orange pollen, but many of those older flowers had no pollen visible on the female parts and presumably had not been pollinated. Furthermore, those older, darker flowers often still contained a full load of pollen on the male parts, showing that no bee had come to take pollen away.

The upshot of these observations is that the story of the color change in the banner petal as a signal that guides a bee to the most appropriate flower may be just a story, in the case of our local species. Or else, we have a lot of very naïve bees. At least, a more thorough investigation is warranted.

There’s a second puzzle about lupine too: As an adjective, the word ‘lupine’ means wolfish or wolf-like. Now what in the world (or out if it) do wolves have to do with these flowers? Maybe nothing; maybe the name is just a distortion of some earlier word. In any case, I have found no good, clear explanation for the name of this plant.

A different sort of confusion arose during a recent visit to Cowee Meadows, where we noted at least seventy species of flowering herbs and shrubs along the trails and in the expansive meadows. This is a really rich place! This year we found a flower we hadn’t seen before. Down along the rocky beach, we found a stand of white, daisy-like flowers. These appear to be a species of Chrysanthemum, sometimes called the Arctic daisy. These daisies have several other common and scientific names, so the taxonomy is bewildering. Whatever it is called, it is a native species that is not to be confused with the common invasive oxeye daisy that occurs as a weed along roadsides and other disturbed sites. In any case, finding a new (to us) species was fun!