The Silithari are actually a species from AI Dungeon, built into the "Planet Omega" stock world. They have no canonical appearance, though, with this being their World Info entry:

The Silithar are bipedal insectoids. They have an innate technical aptitude and form a large portion of the Seekers’ armies. They have a natural desire to slave over others, detesting the “weakness” of most other races. Their natural venom is a clear blue and it can paralyze most opponents for up to two days.

So to decide what they looked like, I put in what few tags they did give us, as well as putting "Silithari" in a LOT of curly brackets. (13 pairs, I believe), knowing it wouldn't have any data to draw from but wanting to see if it tilted the RNG in a consistent way.
A species made for a bot should also be designed by a bot, shouldn't you think?