Spiders.
Before you say spiders cannot be domesticated, but they can be utilized:
Poison -> spears, darts, arrows = lots of death for their enemies and hunting
In regards to poisons, sure. With enough patience, you could probably do that.
Silk -> Spider silk can be woven into fabric that is stronger than most fabric. With the right weave and the right TL leap you could have a bullet-proof vest
The problem with spiders is that you would need a
lot of them to produce the amount of silk you'd need. It's hard enough to do that
now.
Given enough mulberry leaves, silkworm caterpillars are quite happy to be near other silkworms; domesticating them is
easy. Put spiders together, and they will eat each other.
It's sooooo much more cost effective to make silk with silkworms than with spiders, it's not even funny. There are reasons why there are transgenic goats that produce spider silk proteins in their milk.