Preheat oven to 375°. Using small pieces of foil, make forty 1/2-in. foil balls for shaping spider legs; coat lightly with cooking spray.
For filling, mix first four ingredients. On greased baking sheets, pat five biscuits into 3-1/2-in. circles. For legs, cut each of 10 breadsticks crosswise in half; cut each piece lengthwise in half. (Reserve remaining breadsticks for another use.) Attach eight legs to each biscuit, twisting and pressing onto pan to adhere. Tuck a foil ball under the center of each leg.
Spoon filling over biscuits. Fold cheese slices into quarters; place over top. Pat remaining biscuits into 4-in. circles; place over cheese, pressing edges to seal.
Whisk together egg yolk and water; brush over tops. Attach olives for eyes; fill centers with pimientos. Sprinkle with poppy seeds.
Bake until golden brown, 15-20 minutes. Serve warm.