Chapter 5 “Sandman” has 8 Hidden Spiders:
Hidden Spider 33 — You can find the 1st one right at the beginning to the left side of the area crawling alongside a wooden wall underneath the building.
Hidden Spider 34 — You can find the 2nd one in the second area with another Sandman tornado. The second platform you come across as you cross the sand, it will be crawling alongside the wall of this platform up top.
Hidden Spider 35 — You can find the 3rd one right near the end of the second area right before you have to knock down the water tower into Sandman’s tornado. It will be crawling on top of a platform right near a tanker with the number 36 written on it.
Hidden Spider 36 — You can find the 4th one inside the tunnel which the entrance caves in after entering. This is the same tunnel you enter after the second area and knocking down the water tower.
Hidden Spider 37 — You can find the 5th one during another boss fight with Sandman. It will be all the way towards the right side of this area crawling on the wooden ground. It is also right near a caved-in tunnel, and one of the water barrels conveyors.
Hidden Spider 38 — You can find the 6th one in the third large area with another Sandman tornado. This is right before the first (but second overall) water tower in this area. It will be crawling on a wooden wall near the tracks, opposite side of the water tower.
Hidden Spider 39 — You can find the 7th one on a wooden wall next to the last platform in the third large area. This platform has the final and second water tower in this area (third overall). Make sure to grab this Hidden Spider before you knock down the water tower onto Sandman.
Hidden Spider 40 — You can find the 8th one in the area when you come across the rock drill and have to save the civilian at the end of this area. It is right below the platform the civilian is on, crawling on a wooden wall below. The best way to grab it, is to drop from the platform above then recover yourself when you’re falling.
This video shows how to find all 8 Hidden Spiders in level 5 “Sandman”:
Chapter 6 “Vulture” has 8 Hidden Spiders:
Hidden Spider 41 — You can find the 1st one right near the beginning on the 2nd level building crawling around the wall underneath the 3rd story balcony. This is just after you come across a 2nd enemy that is on a balcony that is in between the two building in the alley.
Hidden Spider 42 — You can find the 2nd one directly ahead from where you found Hidden Spider #1. It will be on the other side of the archway crawling on the wall right above a flaming barrel.
Hidden Spider 43 — You can find the 3rd one inside of the Creole Club, smash the wooden shelving unit to reveal a small hidden room. It will be crawling around the wall covered in newspaper in the back.
Hidden Spider 44 — You can find the 4th one on the right side of the Puritan Hotel rooftop. This will be just after you have to avoid getting hit by the train and just before the area to save civilians.
Hidden Spider 45 — You can find the 5th one just before the area where you have to save the civilians. Turn around after the cutscene, it is near the top of the smoke stack.
Hidden Spider 46 — You can find the 6th one crawling on the high way near the civilian you have to save to the far right side from where you started this area. This is near where you just found Hidden Spider #5.
Hidden Spider 47 — You can find the 7th once you are inside the first building you enter after saving the civilians in the burning building. It is going to be in the next room after the hallway with the pipes in them. It is crawling on the wall above the entrance as you go in.
Hidden Spider 48 — You can find the 8th one in the same room you found Hidden Spider #7 and that has 4 generators. It is in the loading dock crawling on the wall above 3 pallets lying on the ground below.
This video shows how to find all 8 Hidden Spiders in level 6 “Vulture”: