A Northwoods Almanac for August 21 to September 3, 2015
Honeydew – And I’m Not Talking Melons or a Retiree’s To-Do List
I’ve received many phone calls in the last few weeks from folks perplexed and distressed by the sticky sap that has been covering their car windshields, decks, lawn chairs, etc., every morning for weeks. Many of the callers say they’ve lived here or visited for decades (one caller said 50 years!), and they had never experienced anything like this before. They’re able to wash the sap off with water if they’re under hardwood trees, but if the overhanging trees are conifers, then the issue gets stickier, as it were.
It turns out the cause of the sticky mists are tiny aphids and other species of scale insects that feed on sap in the tree leaves. The insects take in much more sap than they can hold, apparently requiring this extra volume of sap in order to get all the nutrients they need. They take out what they need and then excrete the excess, the fluid falling in a mist kindly referred to as “honeydew.”
In researching this, I learned that in some years, hikers are covered in a honeydew rain by the time they’re completed a hike, and find themselves being buzzed by yellowjackets. Yellowjackets collect honeydew from the scale insects infesting a tree and make forest honey out of it.
Further research found that some species of ants “farm” aphids. The ants eat the honeydew the aphids release, and then protect the aphids from predators. These “dairying” ants actually milk the aphids by stroking them with their antennae. This mutualistic relationship benefits both species, and is a great example of co-evolution.
A truly amazing variation in ant–aphid relationships involves Niphanda fusca butterflies and Myrmica ants. The butterflies lay their eggs on plants where the Myrmica ants tend the aphids. The eggs hatch as caterpillars, which then feed on the aphids. The ants, however, don’t defend the aphids from the caterpillars, because the caterpillars produce a pheromone that makes the ants think the caterpillar is actually one of them. So, the confused ants actually carry the caterpillars to their nests and feed them. The caterpillars, in turn, produce honeydew for the ants. When the caterpillars reach full size, they form cocoons and emerge after two weeks. The ants now attempt to attack the butterflies, but the butterflies exude a sticky substance on their wings that disable the ant’s jaws, enabling the butterflies to take flight. They return later to lay their eggs, and the cycle begins again.
Wow! This stuff is better than fiction.
Anyway, there’s nothing homeowners can do about the honeydew mist at this time of the year. The good news is that while the insects can stress the trees, they are not particularly harmful – just a nuisance to those walking, living, parking vehicles, etc. under them. Do a google search for “photos of scale insects on maple trees” to see some crazy-looking pictures of these insects.
We have a paper wasp nest under our deck, which is causing some distress to us as well as to the hummingbirds, which are quite unhappy sharing their feeders with the sugar-seeking wasps. These fellows are yellowjackets, though which yellowjacket species I don’t know. Wisconsin boasts thirteen different yellowjacket species, all of which are slender and slightly shiny, and most of which have distinct yellow and black banding patterns on their bodies (a few species are black and white). They aren't covered with fuzzy hairs like bees, so they are actually wasps.
Yellowjackets are renowned for the beautiful architecture of their nests. From tree pulp, they scrape, they chew, they mix, and then they build masterful papery globes. They spread the mix in thin strips, forming stacks of combs. Depending on the yellowjacket species, the nest may hang from a branch, nestle inside a wall crevice, cling to the side of a house, or be concealed underground in a cavity (we have a second nest that was built inside one of our bird houses). The nest is occupied for only a few months each year, then abandoned.
To feed their sugar addiction, yellowjackets search out the honeydew produced by aphids and scale insects. Protein comes from predating on other critters like caterpillars, spiders, centipedes, flies and damselflies. Yellowjackets also scavenge from carrion, sharing a dinner table with eagles, coyotes, and crows. But humans are their favorite species to scavenge from. We offer them all sort of sweet entrees, from soda, to picnics, to beer, to compost and garbage. We offer the low-hanging fruit for yellowjackets.
That would not be a big issue if yellowjackets weren’t able to sting multiple times and live on, which is why these wasps apparently feel free to be aggressive. Since they aren't necessarily risking their lives to sting, yellowjackets will readily defend themselves from what they perceive as an attack (i.e. a mouth drinking from the soda can that they are trying to extract some sugar from).
Ah well. It’s important to remember that most wasps are beneficial, feeding on other insects like flies, beetles, caterpillars, and other garden pests. They also pollinate many plants. So, in the grand scheme of things, they’re good guys, just as long as you don’t inadvertently slurp one up while drinking soda.
White Pine Cones
In numerous hikes this late summer, we’ve crushed a lot of white pine cones underfoot. You may recall that last autumn was a bountiful year for white pine cones, and since white pine cones take two years to mature, that largesse now resides, or is still falling, onto the forest floor.
No conifer tree bears a heavy cone crop every year. White pines bear good numbers every three to five years. Good red pine cone years often have an interval of five or more years. And while good crop years are one thing, and good germination yet another, avoiding the appetite of white-tailed deer is the big key – white pine is well-loved by deer.
White spruces are also starting to drop numerous cones, indicating a good year for them. Unlike white pines, their cones mature and drop in the first autumn, so something obviously went right for white spruce this spring.
Keep an eye skyward near dusk for migrating nighthawks, particularly over open fields and low over highways. I saw the first report of flocks migrating through the Northwoods on 8/16.
Nighthawks are aerial acrobats, darting in flight more like butterflies than birds. To ID them, look for the sharp-angled wings and the white slash across their wings.
The Secret Lives of Bumblebees
“Science on Tap” resumes in Minocqua on Wednesday, September 2nd, 6:30 pm, at the Minocqua Brewing Company. Jeremy Hemberger, a UW Madison graduate student in entomology, will give a short presentation on his current research on bumblebees, their habitat, and lives.
Since seventy percent of the world’s crops benefit from insect pollination, and bees are the best at this endeavor, understanding what landscape helps them thrive is crucial. Come early and join the usually large crowd to learn how bees are followed using new technologies, including RFID (radio frequency identifier tags).
Can’t Identify A Sound?
Over the years I’ve had many folks call me to ask if I can identify a sound they heard during the previous night. I often had no idea what it was, so I wasn’t terribly helpful – there’s lots of mystery out there.
But now there’s some hope for that mysterious ID. If you’ve heard a sound in nature that you can’t identify, capture a recording and send it in to NPR’s new series, “Decoding Nature” at email@example.com. If your sound is selected, experts at the Cornell Lab of Ornithology will try identify it for the radio segment.
Can’t Identify a Feather?
I found a website that helps greatly in identifying feathers: “The Feather Atlas.” Go to http://www.fws.gov/lab/featheratlas.
Hummingbirds Gaining Weight for Migration
Keep those hummingbird feeders filled over the next few weeks – hummers are clearly getting ready to migrate. During migration, a hummingbird's heart beats up to 1,260 times a minute, and its wings flap up to 80 times a second. To fuel this high level of energy, a hummingbird will typically gain 25-40% of its body weight before it starts migration.
Hummers have to leave early because they depend on insects for protein, and most insects die in the first hard freeze. Their initial urge to migrate is triggered by the shortening length of sunlight and has less to do with temperature or the availability of food – hummingbirds actually migrate south at the time of greatest food abundance.
For first-year hummers, there's no memory of past migrations, only an urge to put on a lot of weight and fly in a particular direction for a certain amount of time. The adult hummers leave before the juveniles. Once a young hummer learns its route, however, it may retrace it every year for as long as it lives.
The full moon occurs on 8/29. Known by some as the “Woodcutter’s Moon,” it’s a reminder to get the wood cut and stacked, because the “W” word is not that far off.
"August is tomatoes ripening and the insistent note of the cicada punctuating the heat of midafternoon. August is the smell of corn pollen, and the taste of roasting ears, and the stain of blackberry juice on the fingers. August is a languid river and a springhouse brook reduced to a trickle. August is the first sprays of goldenrod in the uncut fencerow. August is fledglings all feathered and on the wing. August is the heavy grapes in the vineyard, and the lacy leaf where the Japanese beetle feasted in metallic glitter; it is the algae on the pond and the fat green thumbs of cattails in the swamp and vervain in full bloom. August is a hastening sun, earlier to bed and later to rise. August is Summer thinking of the cut and color of her Autumn costume." From Hal Borland, Sundial of the Seasons