one of the spiders i blasted had an extra loot item on it, it looked like a bucket of guts. can't remeber tho, i'll repost when i have a pic of the item and its name (i still have it)
If you plan to take up baking, or already have, 1 spider legs + 1 frosting (available in Halas from Sissia, upstairs in McDaniel's Smokes and Spirits in Halas) = Woolie Spider Crunchies, a meal which gives the eater sv fire -1, sv cold 2. I'm a very low-level baker and my success rate is very poor so far, but I'd guess one out of every 7 or 8 attempts I manage to make food - regardless of success, I'm accumulating baking experience.
This does not apply to spiderling legs, which I know of no use for. There is a site that says that any stackable spider-like legs will work but I get "cannot be combined in this container" with the spiderling legs. The community oven is located outside McDaniel's in Halas, or if you want to make Woolie Spider Crunchies on the go, another vendor upstairs sells Spits for on-location baking.
If you have some spider or spiderling silk, tailors can make cord and thread out of spiderling silk, and the spider silk is used to make swatches (lots of stuff). If you have some, feel free to trade them to me (i always have plenty of armor to trade 8) ).
The silk can also be used to make raw silk armor, i wore some of this armor up into the 30's levels. Very light weight, and better than having an empty slot
You can resist their poison attacks with even a mediocre save in Poison. It's only truly dangerous if you have less than a bub of health. Their silk is worth good coin if sold to tailors and some rogues have been known to purchase the venom sacks. They were still giving exp to me when I was lvl 11.