Went back to where I'd found sawfly larvae (185488439) being parasitized by wasps (185488442) on Interior Sandbar Willow (185488436) 4 days prior.
Fewer sawflies - and a lot more wasps! I was just astounded to see at least 4 wasps on a single larva. Some were clearly ovipositing. There was some variation in size though; I wondered whether there was >1 species present, or whether male(s) were hanging out on the larva waiting for females to arrive.
Had to feel a bit sorry for the larva, actually. Not only was it covered in parasitic wasps, there was a tiny mite crawling on it. (I was definitely having an off day and struggling to get any decent shots of the wasps - didn't even try on the mite.)

Found on American Sycamore (182127709).
Originally seen 3 days prior (182127713), still holding onto the remnants of its spider host. Revisited 2 days ago (182127718); then it was spinning its cocoon and I could still see the larva moving inside. One day ago (182278132) I could still see some movement, but it seemed more compressed and less active - possibly a pupa?
Now it seems still.

ID tentative; improvement welcomed.
This was weird. The temperature had fallen and dusk was gathering when I noticed something waterskiing to shore. And another - and another! I assumed that some species with an aquatic juvenile form was molting into adults. But why do that in chilly weather at a colder time of day?!
It was hard to spot them where they stopped, and harder to get to them for photos because they remained in debris offshore. The low light didn't help, either.
I saw a lot of what appeared to be failed molts, but couldn't be certain that they weren't still working on it. Couldn't read the wing venation well, either - possibly because they are tenerals?
I filmed one coming in, slowed it down and made a GIF.

A large infestation on Salix interior on banks of the Red Deer River. The infestation was highly localized to a small area. There were many willows growing along the river bank in many places but I only saw the beetles in this one spot. I collected a series for the Royal Alberta Museum under a research permit.
The last image shows the characteristic feeding damage. I also have a nearby observation of the host plant: https://www.inaturalist.org/observations/139076833

Lam Tsuen Valley, Tai Po, Hong Kong

These solitary bees are thieves - they steal nectar from the base of the flower by stabbing through the nectary, rather than using the conventional method of collecting nectar (and getting a dusting of pollen), so are no good for pollinating flowers.
update (see comments)
"These bees also collect pollen, so they are important pollinators, in fact quite important because of their abundance"

Arethusana arethusa, Coenonympha pamphilus, Boloria dia, Lysandra coridon, Plebejus argyrognomon (aberration :))

Feeding on fox scat full of blackthorn berries. :)

Update: observations for each species are
https://www.inaturalist.org/observations/129558373
https://www.inaturalist.org/observations/129558454
https://www.inaturalist.org/observations/129558537
https://www.inaturalist.org/observations/129558585
https://www.inaturalist.org/observations/129558618