It was so stinking hot when I wrote this that I got a bee in my bonnet to save it for a dreary winter day. At the time I had plenty to write but not enough time. Now I’ve got plenty of dreary winter days.
Aug 18, 2016 at a landing on the Umpqua River
It’s a hot, lazy late summer day and its only going to get hotter as the day wears on. Dale and I have come to the edge of the Umpqua River to do a little ‘bugging,’ i.e. photographing insects. Today temperatures are supposed to reach 103; tomorrow 111! I don’t think I’ve ever been in 111 heat ... and I don’t intend to tomorrow. Fortunately we can head to the Oregon Coast when it gets beastly hot. Hot air inland pulls cool air off the Pacific Ocean. It might even be foggy there.
Today, while wandering along the riverbank, I aim for the cooler spots. I find toad hoppers right down near the water, damsel flies are perched on long grasses near shore, a spider on its web in the shady coolness of the trees; but, wouldn’t you know, the tiny wasp that catches my attention is in the hottest spot – right down on light, dry sand, tucked amongst heat-absorbing boulders. When I kneel to photograph the little wasp, my knees burn on the hot sand -- just bearable.
I don’t think the wasp likes the heat either. It frequently lands on the sand, but only for a moment. He is a busy little fellow and very skittish when I point the camera at him. I back off and watch a little before trying to photograph him again.
The wasp stays put much longer when it lands on a wisp of dried grass or a tiny forb about 4 inches above the sand. I’m sure just those four inches make a difference in temperature.
Bah! Sweat is running a big rivulet down my back, my knees burn, and the little wasp still challenges me. Finally I give up the insanity of photographing it. I do have a good face shot, but no good body shot.
I move on.
Not fifteen feet farther I find a similar wasp. I’ll approach more cautiously this time. I think about where he likes to land, the direction of the sun, and where my knees will hit sand, not rock. With the lens I’m using I can only focus if the end of my lens is about two feet from my subject. I ease down and wait for a moment so the wasp can get used to this big blob (me). The wasp is less than half the length of the pink part of my thumbnail. I’ve measured my thumbnail (15 mm). Knowing the size of insects helps me look them up.
This individual is just a wee bit more cooperative. The sweat still runs down my back, my knees still burn, but I finally get a series of shots.
Time to head for the shade!
I head back to the shady picnic table near where we parked. At the table dappled sunlight dances on my page. A weak breeze feels ever so delicious on my sweaty brow.
It’s a sane 85 degrees here, but I get to wondering just how hot that sand is. Being married to a soil scientist has its perks. Tucked in the visor of our car is a soil thermometer.
A soil thermometer is a gauge mounted on a six inch metal post. Usually it is stuck into the soil, but I want the surface temperature. I slip it under a thin layer of sand and I shade it so the sun can’t heat the metal – 137 degrees! No wonder my knees feel fried!
Aug 27, 2016
I’m back at the same spot. I thought Bug Guide would verify my tiny wasp as a ‘Microbembix’, but the answer was Philanthus, a beewolf. Needless to say its name says a lot about its prey – the tiny wasp preys on tiny bees. Adult beewolves feed on nectar, but they provision their nests with small bees, possibly wasps too.
We arrived at James Wood Landing mid morning. The Umpqua is lovely at this time of year. Tall, cool forest rises from the slopes. The river runs clear and green. Patches of willow and lush grasses decorate the water worn rocky riverbed that is exposed at this time of year.
I immediately head out walking upriver along the river bank. The spot where I photographed the beewolves on Aug 18 is reasonably close by and I think it is warm enough for the insects to be flying. But mostly I see yellowjackets searching over the warm sand. No beewolves.
I keep going. I wasn’t aware how easily I can follow the river along here. Much of the path is river sand, but cluttered with human tracks. I check a couple of spots off the beaten path. Not much happening. The openings are warming up nicely, but everything in the shade is still cool. Am I too early? Have the yellowjackets greatly reduced the other insects?
I’m about 1/8 mile upriver when I come to a big patch of sand just uphill from the trail. It is a-buzz! Sand wasps catch my attention first, but I also see the tiny beewolves.
At first there is so much to watch it is hard to bring order to the activity. Not many beewolves, but those that are here don’t appear to be hunting. They spend some time on the sand and some time on either grass or a forb about four inches off the sand. Perhaps they are males guarding their territory.
The sand wasps are chunky and significantly larger. I suspect it would take 6-8 beewolves to weigh as much as one sand wasp. Maybe more.
The sand wasps have dug several holes in the loose sand. While they dig, the sand often caves in, but no matter. They are the little badgers of the insect world. Sand flies in a blurr. Often they are just reopening their doorway and quickly disappearing into a hole that they’ve already dug. Both sand wasps and beewolves dig long chambers into the sand and lay their eggs inside. Odd to think that right now (February 2017) these nursery chambers are underwater. Winter always brings rain and brings the level of the river up over these sandbanks. I’ve read the wasps know how to line their chambers in such a way to hold air and not let their nursery drown.
Often a sand wasp appears to be empty handed when she return to her burrow, but then I see one bring in a dead tachinid fly and another brings in a drone fly. Two more have come in with prey, but they zip in so quickly I can’t identify the prey. I’ve read that flies are sand wasp's usual prey and, unlike many of the solitary wasps, sand wasps continue to bring flies in while their larvae develop. Most solitary wasps provision the egg chamber with food, seal it up, and their job is done.
I could watch the goings on all day, but my stomach tells me it is time to return to the car for lunch. On the way back I notice a little black poop on exposed river rock, at least I think it is poop. Each has a hard white lump attached. Total length is about 8mm. Another mystery for another day.