Yoh Isogai and I cloned a number of lines from the Tjian lab liquid nitrogen stock of S2 cells back when I was a post-doc in the lab. We selected for adherence because we intended to use them for imaging experiments and picked adherent colonies by hand to clone the individual lines.
I do not know the origin of the parental line culture. The Tjian lab had been using them since at least the mid-80’s. My best guess would be the Rubin lab but this is just a guess.
All of my publications using Drosophila cultured cells since about 2003 have used this isolate. I have given the clone to a number of other labs over the years including the Rodal Lab, Nelson Lau’s lab- who recently published the transposon landscape of this line-, Don Ryoo’s lab, Sebastian Kadener’s lab, Eric Lai’s lab, and Michael Rosbash’s lab. I do not know if they maintain this line.
We call the line S2c1 for S2 clone 1.