Summon spider summoned spiders within 60 yards (55 meters) of the caster. The variety and size was up to the caster's whim, and the number of the summoned spiders was dependent on the caster's skill. A caster could summon any mixture of sizes and varieties in the swarm he or she summoned with this spell.
These spiders were under the sole but full control of the summoner. They could be made to fight the caster's enemy, they never fled when commanded to do so, and do practically anything if commanded. The one thing they couldn't be commanded to do was to kill each other. When this was tried, the spiders would simply disappear.
This disappearance happened when the spiders died or when control over them was magically stolen.
The spell had an arcane and a divine version. The difference between the two was that the former took longer to cast but could be maintained longer. Also, the divine version needed no material component.
The spell required somatic and verbal components and material ones in the form of a bag, the size of which did not matter; a small candle, taper, or lamp, which was not needed to be lit; and a spider leg or an entire spider corpse.