Now this is certainly a konga-line that will get a reaction from you, especially if you get too close.
I came across this three meter progression of hairy worms yesterday and I thought I would share;
These hairy worms are a larvae stage of the Anaphe reticulata moth also known as the reticulate bagnest moth, and these processionary marches are all a part of their survival strategy.
The bagnest moth gets its name from the baglike silk cocoon that it emerges from before it starts laying its eggs on trees and shrubs with palatable leaves in proximity. However during the dryer times the hatching worms will feed on the available food for as long as possible and then would head out to find the next food-source. That is when these processionary caterpillars can be seen in action.
This worm trail is normally instigated by a leader who makes use of a silk trail as well as pheromones and chemical clues for the progression to follow, if at any time the line gets disrupted, the entire progression will come to a standstill until a new trail can be formed.
These long lines creates safety in the illusion of them being one big predator in stead of single worms, and this helps protect them against attacks of smaller birds. On a ground level, their very toxic hair helps them ward off any other living threat that comes too close. If you come into contact with the hairs you can expect a range of reactions - such as; mild inflammation and irritation, to severe rashes and anaphylactic shock, and they are considered dangerously toxic.
When these hairy caterpillars feels threatened or stressed, they are able to eject these hairs in defense, this will then manifest in any open skin f the threat and cause undesirable reactions.
Information partially gathered from: https://africageographic.com