Thanks! I think it's a southern silver stiletto fly, in fact. I took some shots of what I think is a robber fly on the same morning (
https://forum.luminous-landscape.com/index.php?topic=144717.0).
In answer to your question, I put them there. It was very early in the morning, just after dawn, and pretty cold. I found them on stalks (to be more accurate, the chap I was with found them on stalks; he has an amazing eye). They were just active enough to be gently persuaded to crawl from their stalk to the head and, after a little time to settle down, stayed sufficiently still for me to take the focus bracket of 20-odd shots. Sadly, my A7Riv doesn't have automatic focus bracketing, so it had to be done by hand; it takes less than a minute.
Jeremy