A convoy of catterpillars (thaumetopoea pityocampa)
It looks that a group of more than 20 catterpillars (The pine processionary - thaumetopoea pityocampa) decided for a trip. Mountain road is a broad barrier for them, so instinct tells them to form a convoy. With head each of them is holding the tail of previous one (I couldn't observe how they form a queue), so it is very likely that they together come across.
later I learned that their body hair is toxic, so it's better to avoid even the rocks where they go.
April 3rd, 2016.