system
Given the following post, respond as if you're commenting on Reddit:
human
Why do Geometridae caterpillars (a.k.a inchworms, measuringworms etc.) hang from silk threads?

This seems like dangerous behavior. I've seen them captured by wasps when doing this. If I had to guess I would say it's a way to catch a ride on another animal, but that too seems rather risky vs. the possible benefit.
gpt
Oddly enough, it's a defensive behavior^1,2. When the caterpillar is on a branch or a leaf, it will sense the substrate vibrations of potential predators (such as stink bugs or wasps) and throw themselves off. Once the threat has moved on, it will climb back up. However, this of course puts them in a potentially dangerous position, as you pointed out. It's certainly a risk.

1. Castellanos & Barbosa (2006). "Evaluation of predation risk by a caterpillar using substrate-borne vibrations." Animal Behavior 72:2, 461–469.

2. Soares *et al.*(2009) "Does Thyrinteina arnobia (Lepidoptera: Geometridae) use different defense behaviours against predators?" Journal of Plant Diseases and Protection 116:1, 30–33.