Unlike rolling stones: not every Myrmecina species actively rolls away from danger (Hymenoptera, Formicidae)

Actively rolling away is a very rare escape strategy in the animal kingdom, which to date has only been documented in a few arthropod and one vertebrate species. One of these arthropods is a West-Palearctic ant, Myrmecina graminicola, which has very recently been demonstrated to actively curb into a ball-like shape rolling away upon disturbance, and to selectively display this behavior only under particular circumstances. We tested whether one of the other three W-Palearctic Myrmecina species, the rare insular endemism M. sicula, exhibited the same behavioral response, using the same experimental approach used for M. graminicola. Our results showed that M. sicula reacted to moderate disturbance by either freezing its body or walking away. Only when the individual lost contact with the substratum, it could curl into a ball-like shape, yet this was significantly less refined than the one displayed by M. graminicola, as the appendages of M. sicula are not tightly kept close to its body. However, M. sicula never performed the active rolling behavior that is readily exhibited by M. graminicola. Ecological, morphological, and phylogenetic constraints may have determined the lack of a developed active rolling escape-strategy in M. sicula. Further investigations are required to assess the presence or absence of this unique behavior across Myrmecina lineages.