Chapter 9 “Juggernaut” has 8 Hidden Spiders:
Hidden Spider 65 — You can find the 1st one crawling on a brick wall on the left side when you fight another group of enemies for a second time. This is after the mini-boss fight with the Juggernaut. You can jump over or smash the wall to get over to the brick wall.
Hidden Spider 66 — You can find the 2nd one crawling on the ground in a pipe after smashing a wall in the next area. This is right after the area where you collected Hidden Spider #1 as well as where the Juggernaut is throwing objects at you from a distance.
Hidden Spider 67 — You can find the 3rd one crawling on the ground in a small room to the left of where you have to web pull the vent off in order to proceed on with the level.
Hidden Spider 68 — You can find the 4th one directly below you crawling on the building wall as you start the area where you have to save the 3 scientists in order to shut off the valves to the fire.
Hidden Spider 69 — You can find the 5th one in the next area after saving the scientists crawling on a building to the left side. You can grab this before or after the cutscene with the Juggernaut. Either jump through broken glass ceiling or go around the ramp, to reach this area and then jump or crawl up the wall to grab it.
Hidden Spider 70 — You can find the 6th one at the basement entrance to the large building you need to climb. Make sure to get this before heading up the large building. It will be at the bottom of the ramp crawling on the ground in between the doors on the median.
Hidden Spider 71 — You can find the 7th one crawling on the wall at the far right side of the building as if you were looking at the building from the area you previously were on the ground. It will be right above and at the end of the damaged scaffolding.
Hidden Spider 72 — You can find the 8th one right near the rooftop of the front left corner as if you were looking at the building from the area you previously were on the ground. It will be near the middle of the building crawling on a window above the scaffolding.
This video shows how to find all 8 Hidden Spiders in level 9 “Juggernaut”:
Chapter 10 “Goblin” has 8 Hidden Spiders:
Hidden Spider 73 — You can find the 1st one crawling on the wall of a building on the right side of the carnival. It is the building right in front of the spinning ride.
Hidden Spider 74 — You can find the 2nd one inside of the first tower to the left side of the carnival. It is crawling on the wall just above the archway.
Hidden Spider 75 — You can find the 3rd one right by where you found Hidden Spider #2 in the tower. It is crawling on the right side of a tent that is on the left side of the carnival.
Hidden Spider 76 — You can find the 4th one inside another tower but this time a little larger at the far left side at the back end of this area of the carnival. It is crawling on the wall above the archway.
Hidden Spider 77 — You can find the 5th one in the far right corner of this first area of the carnival. It is crawling on the side of the towers outside wall. It is also right near a civilian to save.
Hidden Spider 78 — You can find the 6th one right after you exit the carnival tent. It is directly to the right side of you in the corner crawling on top of a cage.
Hidden Spider 79 — You can find the 7th one inside of the cage where the 2nd civilian is locked up in. This is the civilian to the left side of the area where you save a total of 3 civilians.
Hidden Spider 80 — You can find the 8th one inside of the fun house when you reach the upside-down room. Just take the left path up the wall to grab it crawling in between the window and painting.
This video shows how to find all 8 Hidden Spiders in level 10 “Goblin”: