game mechanic Sawblade spawns

[Chickon_20]

I'm gonna design a farm but I don't know how the sawblade locusts spawn. I'm thankful for every information.

[Maelstrom]

My experience is that sawblades only spawn randomly in caves, usually lower elevations. You're likely to see slightly more bells than sawblades but you'll get immensely more drifters than bells and sawblades combined.

I had one exception where a sawblade spawned less than 20 blocks below the surface, which was about 5 blocks ABOVE sea level.

[Thorfinn]

They are insanely rare, at least on hardcore wilderness defaults. This current game, I've encountered exactly 1. It's now January, and I've been spelunking pretty much non-stop since mid fall, there being pretty much nothing else to do...

[Maelstrom]

In my current world I've had precisely 2.  One way back during the first summer.  The second one appeared practically on top of me while mining olivine in the second fall.