My bee-expert colleague Alison Benjamin (whose book A World Without Bees is a must-buy) tells me that my raided nest (see immediately below) is a bumblebee one; not the big Solitary Bee bumblers which grind about like aerial mowing machines, but a smaller variety. People put flowerpots over them to protect them, she says (making sure that there is an exit hole at the top...) My predator is too big for that, so I've temporarily shielded them with a wheel barrow.
And now - Eeek! - what is this?
A caddis fly in the moth trap, that's what. It's nowhere near as threatening as it appears here, but resembles a weedy-looking moth with transparent browny wings. The life cycle of the caddis is remarkable; the female insect lays her eggs on the the surface of my pond, or just underwater, and then the amphibious larvae build little houses of mud and silt as well as tiny traps to catch algae and microscopic pond life.
They pupate underwater and at hatching time propel themselves to the surface where they struggle free and turn into this. Wonderful! Human birth and life is a pretty arduous experience, but thank goodness we don't have to go through all that.
I've never been a fisherman because my boredom-tolerance threshold is too low, but I admire the way they make and use flies. Here's one modeled on a caddis, courtesy of the website of the English Fly Fishing Shop in Morden, Surrey.