There are three rulesets that might apply. Which is up to your GM (potentially with your input).
Ideally to you, your GM may allow an improvised weapon ranged touch attack using your spider.
- Your spider is unharmed (probably; and argument could be made for applying falling damage)
- You throw against Touch AC with a -4 with a range increment of 10
- Whether or not you hit, your GM determines where your spider ends up as there are no rules for where thrown weapon ends up. Likely, they will land adjacent to the target (as per dropping a object) on a hit and on a miss your GM may have it land 1 square away for each range increment thrown (as per missing with a thrown splash weapon)
Alternately, your GM could expect you to attempt to throw the spider into the target's square.
- Make an improvised ranged attack (as above) against AC 5 (landing an 'attack' in a square)
- On a success, your spider now occupies the opponent's square and can attempt its own touch attack
- This has the drawback of potentially (but not necessarily) still incurring an attack of opportunity, and doesn't really help you if that's how your GM rules.
Finally, your GM could force you to roll a Combat Maneuver to Bull Rush or Push your spider. This is the most awkward of the descriptions, but potentially the best by RAW as creatures are not typically considered weapons.
- Make a CMB. You provoke an Attack of Opportunity from the spider which it will decline to take
- For every 5 by which you beat its CMD, you can "push" the spider that number of squares
- If you force the spider into the target's square, and if you don't have the associated Greater (CMB) Feat, they do not provoke Attack(s)
- Note: Your GM may rule that the target still gets an Attack for the spider entering the target's space because this is yet another gray area
- Your spider may make its attack as normal
Remember when negotiating with your GM that this may be something that is allowed because of "Rule of Cool" but also may not be allowed because it could have significant repercussions to game balance and flow. Touch attacks typically require you getting into melee to balance some other aspect of the spell. While not likely to break the game, be understanding if your GM is leery to allow you to circumvent parts like this with frequency.