I actually spent a bit thinking about this so I guess I gotta share it now, but I don't think any of these would be quite adequate.

Firstly, 1. has the trouser seat attaching at the abdomen as opposed to the cephalothorax, essentially limiting the degree of movement those back legs can do, dressed like that, this poor spider would have to drag its hind legs behind it.

Image number 2. Solves 1's problem by presumably coming together on the spider's underside, this is problematic because spiders breathe via a book lung on the base of the abdomen (see below image) and dressing like this would block it.

Show

Now let's have a look at a spider moving around so we can get an impression of the kindsa range of motion they need.

Show

Ok, you see those front legs, they're probing out ahead of the spider in a way that the trouser configuration of 3. would be obstructive so we can discard that one.

I vote 2, we wear pant to cover our butt and sexy part, not to cover our sexy leg.

1. Spring break
2. Interview
3. Pride