The abdomen on the original thing was just too huge for my 3d printer, so rather than shrinking the whole thing down, I split the abdomen in half using Tinkercad, and then spent many hours printing it, using glow-in-the-dark filament.
A shout-out to Audrey2, who designed this awesome spider in the first place.
Glow in the Dark
I tried printing the abdomen sections with no base, thinking that the two sides would match up together better that way, and that theory worked for the 25% sized test print I tried, but full-sized, it warped badly and had to be scrapped. Better to print it with a honking thick base layer (5 layers thick or more).
The thorax requires supports, but the abdomen halves don't. And I printed the legs with supports, though I probably could have gotten away without them.
I printed the abdomen and the thorax with 10% infill, but I thought the legs needed more. As it is, the leg joints are pretty loose, so they're don't provide any support at all. (Though they are flexible, the spider is only but so "poseable," though I bet if I glued the leg joints, it would be fine.) I was able to fit the 4 sets of leg parts in one print. You need 8 sets, total.
All told, I think this print took about 29 hours, not counting the failed or messed up attempts. (ab1 and 2 were about 6h15m each; thorax was 7h; and the legs were 2x 4h45m.)
And I used glow-in-the-dark filament because we use black lights for our Halloween display, but I imagine you can use any color you'd like.
I pulled the original abdomen stl file into tinkercad, and turned it on its side, then I lowered it exactly halfway down through the workplane, and put a huge box shape in hole mode underneath the workplane, and combined the abdomen and the box, which left me with a precise left half of the abdomen.
I'm pretty certain the hidden half of the abdomen was a mirror image of the half I had, but just to be on the safe side, I ungrouped the objects, rotated the abdomen shape 180 degrees and then joined the shapes back up again, generating the right half.
Then, just to be sure that they lined up, I imported the stl files for the left and right halves of the abdomen that I generated back into Tinkercad, and verified that everything was good.
And here's a close-up shot of the finished abdomen, irl.