The second experiment involves putting a piece of dry ice in a plastic container on a white sheet on the ground in a closed-canopy forest. Dry ice emits carbon dioxide, the same stuff we exhale, and it’s what ticks and other pests home in on to locate a nice blood meal. Leaf beds on shady forest floors are cooler and more humid than other areas in the heat of summer. In 15 minutes, the dry ice trap—remember, it’s not moving, just attracting ticks by carbon dioxide—nails a whopping 243 ticks. One takeaway from this is not to take a nap in forest floor leaves, especially in a bathing suit.