Filmed in Yasuni, Ecuador by wildlife photographer David Weiller, these slug moth caterpillars (Acharia Nesea, Limacodidae) can be seen with a pulsing stripe on each of their backs. Phenomenal rainforest background noises complete the video.
So what movement are we seeing within their small bodies? In this blog post for the Frost Entomological Museum, via Dawn Lawson, Penn State graduate student researcher Carolyn Trietsch explains that caterpillar dorsal vessels contract to pump hemolymph from the base of their abdomina to their heads.
While humans have a closed circulatory system where all of our blood is contained in arteries and veins, insects have an open circulatory system where hemolymph flows freely through a cavity called the hemocoel. The hemolymph then gathers in the chambers of the dorsal vessel and is pumped back up towards the head, so that the brain and other major organs can be bathed in the nutrient-rich hemolymph. The hemolymph continues to flow down through the rest of the body, until it gathers back in the chambers, repeating the process.
Previously from Weiller: The Lychen Katydid camouflages.
Plus, two more from Yasuni: Leaf Mimic Katydids uniquely disguised as dead & diseased leaves and butterflies that drink turtle tears for the salt content.