City Creek Nature Notes – Salt Lake City

June 14, 2017

June 9th

First Tarantula and a Fake Bee

7:45 p.m. The jet stream to the northwest has begun to lower temperatures in the eighties and brings cooling evening breezes to the canyon. On this Friday evening, families seeking release from the days of heat fill the first few picnic sites. The heat wave is starting to end, and invasive Yellow sweet clover lines both sides of the road and waves under the wind. But there is no sign of summer’s yellow sunflowers along the road in Pleasant Valley. More soft tufts of pollen float down from the Rocky Mountain cottonwoods and their white down lines the roadside. Evening Black-headed grosbeak calls predominate in the first mile. A 3 inch unidentified dark blue-black dragonfly sails by. A unidentified light brown beetle, that has the shape of a solider beetle, has been seen on the road over the last few weeks. At the rear tip of its shell, there is a diamond shaped darker brown patch. On the road today, the nymph form of this beetle crosses the road. It is bright lime green. A black ant drags a bug twenty times its size to the side of the road.

Planted squarely across the center of a Wood rose blossom near mile 0.3, a member of the Galphyridae family of Bumble bee scarabs. The Bumblee bee scarab is a beetle, not a bee. Its wing shell has four horizontal white strips on the sides and two vertical white stripes on either side of the centerline. Its bee-like features are the abdomen that extends past the wing shell and is covered in fine yellow-white hairs. Its thorax is also covered with these fine hairs. Male Bumblee bee scarabs are sometimes found in flowers, as this oddly behaving one is. This scarab appears almost intoxicated. It is oblivious to my presence and seems to relish feeding on the rose’s pollen. Given its lethargic ways, the scarab’s mimicry of a bee might provide protection from predators, but given that birds eat bees, what predator does the scarab’s mimicry deter?

Near mile 0.4, the season’s first desert tarantula crosses the road. It is only two or three inches across. By mid-summer, it will grow to 5 to 6 inches across (August 17th).

* * * *

In Thoreau’s “Journal” on June 9th, 1850, he notes pitch-pine pollen collected on water. On June 9th, 1851, he observes that signs of the season are grass waving in the wind, new leaves on trees, and increasing louder crickets. On June 9th, 1853, he sees the season’s first lily bud and notes white clover is common. He sees starflowers in a meadow and gathers strawberries. He observes a hawk pair. On June 9th, 1854, he sees a lark and notes that the air has a high density of mayflies. On June 9th, 1857, he sees an indigo bird. On June 9th, 1860, he sees water bugs in a stream.

* * * *

On June 9th, 1915, a new reservoir on Fifth South that holds 10,000,000 gallons was inspected, and it will supplemented by a 5,000,000 gallon reservoir at Pleasant Valley (Salt Lake Herald). On June 9th, 1909, the Intermountain Republican reported that a flooding City Creek stream was still carving “numerous erratic channels down North Temple street”. Sandbags and manure was used by crews working under Street Supervisor J. T. Raleigh to create embankments, but this results in large pools of fetid water forming (id). The Tenth South canal overflowed its banks. On June 28th, 1905, the Commercial Club officially turned over the new Wasatch Boulevard to the City (Salt Lake Herald). The boulevard runs up City Creek Canyon, along 11th Avenue to Popperton Place, and then on to Fort Douglas. The boulevard then descends to Liberty Park (id). The Club plans to line the boulevard with trees and stone walls, interspersed with developed parks every few miles (id). On June 3, 1903, as a result of infrastructure improvements, the City had increased its water supply capacity to 28,000,000 gallons per day (Salt Lake Telegram). One hundred and thirty-one miles of water main pipe has been laid in the city, including City Creek Canyon (id). A city ordinance regulates residents sprinkling their lawns. The High line system in City Creek brings water to Popperton Place. On June 9th, 1877, the Salt Lake Tribune recommended City Creek Canyon Road for scenic carriage rides.

November 3, 2016

November 3rd

Helicopter Seeds

5:00 p.m. After a major storm on October 31st that involved wind gusts up to thirty-five miles per hour, today parts of the road are still covered in the lobe shaped seeds of Boxelder trees. The seeds are about three-sixteenths (4mm) in diameter, but are attached at the end of a half-inch “wing”. Overall, the seed and wing give the impression of a musical note. The seeds hang in symmetrical pairs on a catkin, a collection of about twenty seeds. Along the road in the first mile, there are many of Boxelders up to fifty feet in height that are covered in catkins. I walk up to one to pull a couple of seeds off, and each seed is surprisingly still strongly attached to its catkin, even though the tree is leafless. I can see why it took thirty-five mile per hour winds to dislodge the seeds that are on the road. I raise one above my head let it go. It starts to rotate quickly and like its cousin, the maple seed, it “helicopters” down to the ground. Testing several Boxelder seeds, they travel an average trajectory at about thirty degrees from vertical. As any middle or high school geometry student can tell you using a 30-60-90 degree right triangle, this means that a seed released from the top of a fifty foot tree might travel twenty-five feet horizontally from its parent tree. This is just enough to land outside the canopy of the mother tree.

During a wind gusts on October 27th, as I jogging past Boxelders near picnic site 6, a few of these “helicopters” would dislodge and float down will a light rain. One was freed from the highest branch by a first gust of wind, and as it floated to eye level, a second wind gust blew through. With that burst of wind, the helicoptering seeds stopped in mid-air and rose slightly, but as the gust diminished, it resumed its descent to the road.

Until relatively recently, the aerodynamics of these flying seeds was a mystery. Using the same principles of flight that govern birds and jetliners, the seeds should technically not float or “helicopter” slowly to the ground. The seeds should drop like a stone. Solving that mystery also explained other instances of creatures that should not fly and should not be able to hover, including several found in the canyon, i.e. – bees, dragonflies and hummingbirds.

In 1991, Lentink at Wageningen University of the Netherlands, Dickson and their colleagues determined that helicoptering maple seeds had a different mechanism of flight than that used by bird or man. As the seed helicopters, the leading edge of the seed’s wing generates a small, horizontal tubular vortex over the wing. This generates a low-pressure vacuum that lifts or sucks the seed upward. Unlike a bird, the wing has no familiar aerodynamic lifting shape. In normal flight like that of a bird or airplane, a smooth laminar flow over a wing’s special shape, similarly generates low-pressure above the wing, and the relatively higher pressure under the wing then lifts the wing and plane or bird into the sky. These horizontal vortices are called leading edge vortices or LEVs.

You may have seen analogous vortices when using a paddle in the water, when moving your arms while standing a pool, or when a plane lands through fog. Horizontal vortices form off the tips of paddles, your arms, or the tips of an airplane’s wing. In the case of the seed, a spinning vortex forms over the entire length of the wing’s flat surface.

In 1996, Ellington of the Vrije University in the Netherlands and his colleagues extended this concept to explain how many insects, like bees, moths and butterflies, can fly when aerodynamically, they should be unable to do so. They found the beating wings of moths generating the same leading edge vortices seen in helicoptering maple seeds. In 2000, Z. Jane Wang at New York University modelled flapping insects wing and noted that for some insects, two counter-rotating vortices are formed. One is a higher pressure vortex under the wing and it pushes up, and the second is a lower pressure vortex that “sucks” the insect up. In 2001, Lauder at the Harvard University built mechanical insect wings in order to better model the leading edge vortices. In 2004, Adrian Thomas at the Smithsonian Tropical Research Institute and colleagues studied dragonflies tethered inside wind tunnels, and they imaged the counter-rotating leading edge vortices (id. Fig. 11). In 2011, Liang and colleagues at Purdue University built mechanical wings with rigid veins similar to those seen in both Boxelder seeds and dragonfly wings, and they found that the ridge veins increased flight performance.

Wasps, bees and dragonflies have a different number of wings. Wasps only have two wings; dragonflies and bees have four. Bees have smaller fore-wings that lock into the larger back wings to form a single wing surface during normal flight. Only the dragonfly has two sets of independently moving wings, and only it moves the wings out-of-phase: while one wings goes up, the other flaps down. The dragonfly can rotate the angle of attack for each wing independently. In 2008, Z.J. Wang noted that the out-of-phase beating gives the dragonfly additional-enhanced lift. These results of Ellington, Lauder, Wang and Thomas give a clearer picture of how the dragonflies seen in the canyon hover and do their amazing acrobatic maneuvers (August 11th).

In 2005, Warrick at the University of Oregon and colleagues showed how hummingbirds also use leading edge vortices to feed while hovering in front of flowers.

In conclusion, the canyon currently hosts many examples of where nature has solved the problem of flight and hovering using leading edge vorticies instead of a bird’s flapping aerofoils or man’s propellers: Boxelder seeds, maple seeds, Variegated Meadowhawk dragonflies, red-rumped central bumble bees, Bald-faced hornets, Black-chinned hummingbirds, and several moths, butterflies and other flying insects. The first dragonflies, the massive Protodonata with 30 inch wingspans, appeared in the fossil record 325 million years ago. Flowering trees first began to dominate forests in the Cretaceous period beginning 145 million years ago, and they co-evolved with bees. Hummingbirds appeared 22 million years ago (McGuire et al. 2014).

Today in the canyon, even though the Boxelders where hammered by the strong winds, only a small fraction of their catkins were dislodged. Most Boxelders are still thick with seeds, and I can still look forward to more future showers of helicoptering seeds on windy days.

October 21, 2016

October 21st

Smart Trout

1:30 p.m. At the water striders’ pool at picnic site 5 (Sept. 12th), I see the first brown trout in the canyon for over a month. The light filtering through the trees brings out the molted spotting on its upper skin. This trout hides in the pool under a branch that dips across the pool’s middle. I remain motionless for a minute and in reply it station-keeps with one eye gazing at me. When I make a sudden move by taking one quick step the right, the trout frantically swims under a stream-cut overhang that is covered by dense foliage. It has excellent eyesight even through the water’s surface. In one corner of the pool is a single water strider, and these are what the trout has been feeding on. Later, the trout is joined by two smaller companions.

Today, the yellow tube of falling leaves (Oct. 11th) is over and temperatures have risen into the sixties. The predominate colors between mile 0.0. and mile 2.0 is brown and grey. Like the last sunflower (October 14th), this is another marker of seasonal Fall change. Because of the temperature, insects have again become active, but I count only thirty on the road, including possibly two Yellow-head bumble bees with black rumps, a Variegated Meadowhawk dragonfly, a large unidentified blue dragonfly, and, in the box at picnic site 11, a sole European Paper Wasp (see Oct. 11th). These rare late season insects are now more visually striking; they provide the only accents of bright colors now that the leaves have fallen. Crickets are still heard in meadows and forest undergrowth and some have come to die on the road. At picnic site 12, a woodpecker can be heard but not seen. Common woodpeckers in the canyon that drum on trees are the Downy Woodpecker (Picoides pubescens) and the Northern Flicker.

Together, they will swim upstream to join their mates at a shallow fifteen by twenty foot pool below an outdated flood gate at mile 2.8. A regulatory “no fishing” sign on the sluice box protects them from humans. During the winter, ten or fifteen trout can be found there, resting in water so cold that it would kill a person in two or three minutes.The next marker of the seasons, as winter storms reappear at the beginning of November and December, will be season’s end for the flying insects, season’s end of the crickets, and the falling of the last remaining leaves during a heavy snow storm.

October 8, 2016

October 8th

Filed under: Dragonfly, Variegated Meadowhawks — canopus56 @ 4:14 pm

True Name of the Dragon

10:00 a.m. At various times, I referred to dragonflies, but those references were generic and were without a identification of a specific species. On July 29th, I described dragonflies flying in a B-25 bombing formation, and on August 11th, I noted a dragonfly feeding frenzy. On August 22nd, I observed cliff swallows feeding on dragonflies. Dragonflies move so fast that a certain identification is impossible and they rarely cooperate by conveniently resting on a leaf or stalk.

This morning, insects are still recovering after the storm of October 5th, and a few dragonflies, cabbage white butterflies, and moths can still be found. However, because the overnight temperatures have been in the 30s, they are all sluggish. In the cool morning air at mile 1.2 and 1.6, I find two separate dragonflies sunning themselves on the road. They are so punch-drunk from the cold that they do not fly off when approached.

They have the clear perpendicular wings that are the mark a dragonfly, and their abdomens are segmented in brown and pale yellow stripes. Dragonfly eyes are unique and if they have 10,000 to 30,000 lenses in their compound eyes. This allows them to perform the precise acrobatic maneuvers needed to catch small insects. In contrast the house fly has 3,000 to 5,000 eye lenses in its compound eyes.

After taking a photograph and doing some research, field guides instruct that these dragonflies are immature Variegated Meadowhawks (Sympetrum corruptum). The meadowhawks are a member of the skimmer dragonfly family (Libellulidae), and they differ from other families in that they have a distinctive lobe at the margin of each eye. I unable to distinguish this feature between photographs of various types of dragonflies.

The term meadow “hawk” is ironic. Although these hawks are a predominate predator of small insect world, the meadowhawks themselves are prey for the cliff swallow, the scrub jay, the Mountain chickadee, and the Northern flicker.

In the Norse and Germanic legends, knowing the true secret name of a creature gives one special powers, e.g. – the release of the miller’s daughter from the imp’s curse when she speaks his name, “Rumpelstiltskin”. When I return to the canyon tomorrow, I will in the style of a currently popular childrens’ book character, raise my wand and speak the true name of the meadowhawk, “Libellulidae sympetrum corruptum.”  I anticipate that the meadowhawks will continue in their aerial contortions and will remain oblivious to my bidding.


September 26, 2016

September 26th

Just a Short Walk

4:00 p.m. Just a short walk between the Guardhouse gate at mile 0.0 and along the first quarter mile, individual variation in leaf turning within tree species can be seen. Today, in the parking lot at Guardhouse gate are several large horsechestnut trees, and as noted on September 23, their leaves are turning brown at the edges. But a short distance away at picnic site 1, there is another large chestnut tree that experienced the same cold weather, but it remains completely green. Similarly, just past the gatehouse, there is a large, apex narrow leaf cottonwood tree, but 200 yards up canyon, there are two immature cottonwood trees that have completely turned a bright yellow. Within the first 50 yards of the gatehouse, there is a Box Elder tree that has almost completely turned and one that has only begun to turn.

There is some type of ordered distribution to this seeming randomness. I pull out my field note pad, and I am tempted to record a list of road positions, type tree, and percent of leaves turned. I have made such lists in the past for birds and animals in the canyon. But I remind myself that I am here for solitude and not to start another project, and the notebook is put away.

Along the first mile, gnats have returned, but at a lower density, and so their predators, the dragonflies, have also returned. But the dragonfly population is now counted by the tens and not by the hundreds as before the cold overnight weather. The waterskimmers are completely gone from their pool at picnic site 5.

September 24, 2016

September 24th


4:00 p.m. In the afternoon, the storm moves on, the clouds become broken, the air warms, and where the broken clouds create windows, beams of sunlight illuminates individual trees into beacons of color. Which part of the canyon and which tree is featured changes constantly. After an hour, the broken clouds end, the sky clears, and the canyon is bathed in the soft sunlight of Fall. The The ground dwelling crickets seem unaffected by the storm, but only the hardiest individuals of each type of flying insect is out, and this makes it a day of ones. I see exactly one of the entire cast of flying insect characters that are common to the canyon: one gnat, one dragonfly, one red-rumped central bumble bee, one white cabbage butterfly, and one jet black wasp with yellow-tipped tail. Five hundred feet above, a lone raptor that is to far to away to identify soars. As a finish my jog, the lowest part of the canyon is much warmer, and more gnats have returned. It will take a few days of warm weather for the flying insects to fully recover.

Because of the fall colors and because the canyon will be closed to public automobile traffic for six months in another week, city residents have turned out for automobile touring. I stop counting after the fiftieth car has passed. This annual automobile closure restricts the canyon only to pedestrians, bicyclists, and an occasional hunter, and during its winter sleep, the closure allows the canyon to recover.

September 21, 2016

September 16th

Filed under: Colors, Dragonfly, Insects, Maple tree, Meadow Mile 1.3, Moth, Places, Sunflower, wasps, Weather — canopus56 @ 1:26 am

Shriveled Sunflower

5:30 p.m. It has been two days with overnight temperatures in the forties. At meadow at mile 1.3, the roadside sunflowers have shriveled and fallen over. Only a small patch that contains a few blooms remain. But the crickets and the dragonflies have withstood the low overnight temperatures. During the first two miles, there about 200 dragonflies, but only two or three butterflies and moths. At mile 1.2, I notice for the first time, an eight inch diameter wasp nest that is still active, and it is the home of the jet black wasps seen on September 9th. The nest is only 25 feet from the road, and assuming it was built in back in June, I have been unknowingly running past it for about three months.

The low temperatures and moisture have triggered a few late-turning, small maples. I count only 8 maples in the first 2 miles that have turned a fiery red-orange, and these welcome accents of color brighten this year’s otherwise muted annual leaf display.

September 20, 2016

August 29th

Filed under: Dragonfly, Insects — canopus56 @ 11:29 pm

Dragonfly Loop-de-Loop

6:30 p.m. Running down canyon from milepost 2.0, I estimate approximately 200 dragonflies hovering above open meadows and along the road. Near mile 0.9, a gnat is hovering about 10 feet in front of me back lit by the setting sun. A dragonfly swoops in from the right, executes a 12 inch loop-de-loop, snatches the gnat, and then does a victory barrel roll off to the left.

August 22nd

Filed under: Cliff Swallow, Dragonfly, Insects, Meadow Mile 2.1 — canopus56 @ 11:17 pm

Circling Swallows

7:45 p.m. There is a meadow near mile 2.1. The meadow is in shadow, but about 25 feet above the meadow, the horizontal line of sunset is rising up the south canyon wall. In this sunset light and for a swath about three eighths of a mile long, fifteen swallows are hunting by flying in ellipses. Their orbits appear random, but after about five minutes, curiously, groups of five or ten swallows will meet in a small cluster in the sky. Then they will disperse into their individual ellipses. I watch them repeat this behavior two or three times. How they can time this is a complete mystery. Perhaps there is some explanation in mathematics of non-linear chaos. (For the mathematically inclined, the swallows are flying a pattern suggestive of Lorentz attractor.)

What the swallows are hunting is unclear. In the shadowed meadow, a few dragonflies also circle. Do the dragonflies eat small insects and then do the swallows eat the dragonflies? But there are too few dragonflies to support fifteen hungry swallows.

August 17th

Filed under: Dragonfly, Insects, Meadow Mile 1.3, Pleasant Valley, Tarantula — canopus56 @ 11:05 pm

Tarantula Legs

6:00 p.m. At mile 0.7, A lone tarantula is walking across the roadway. Most spiders move so quickly that the action of their legs cannot be clearly observed. In contrast, this 5 inch diameter specimen walks in slow motion. For its rear 6 legs and counting from the abdomen forward, an even-numbered leg on one side moves forward in concert with an odd-numbered leg on the opposite side. It uses its front two legs like antenna, probing the environment ahead. Its abdomen is covered in one of the tarantula’s defensive mechanisms: urticating hairs or irritating hairs. I spend a few minutes with the tarantula to assure that neither a car or a bicyclist ends it.

The canyon opens up after the first mile and dragonflies are evenly distributed over the meadow between mile 1.1 and 1.5. These are the same fifty or so dragonflies that were hunting in a close knit flock back on August 11th. A U.S.G.S. map describes this area as “Pleasant Valley”.

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