Bonjour Alexis,
These are young moths, which I unfortunately know little about. Incidentally, a number of Morpho caterpillars have a similar habit (gregarious on host tree trunks) and approximate size (very large), but those butterfly larvae are somewhat "hairy" and predominately reddish in color – quite different from your pictured chenilles. Please forgive me if you already have this information.
Best wishes,
Keith
Sujet: Chenilles en groupes 
... Merci 
