Mind the Children

Common Pill Woodlouse, Armadillidum vulagre

While some people might say rolling up in a ball smacks of inner insecurities, for the pill woodlouse, Armadillidum vulgare, it is an essential survival response. It is such a distinguishing feature of this isopod that it lends it both its common and scientific names (Armadillidum from the latin armare, “to arm”).  Native to the peripheral Mediterranean, A. vulgare now has a worldwide distribution, extending its range into Europe after the last ice-age and into America and Asia due to human activities. It is mostly found in gardens and other cultivated areas (1).

Common Pill Woodlouse, Armadillidum vulagre showing brood pouch

Sexual activity in A. vulgare is photoperiod dependent. Long days trigger the breeding cycle, while shorter days result in sexual rest (2). Like most isopods, A. vulgare lays its eggs into a brood pouch or marsupium, where the young hatch before being released (1). The number of young carried per clutch by A. vulgare is one of the highest of all terrestrial isopods (3).

Common Pill Woodlouse, Armadillidum vulagre

References:

1. Juchault et al., Acta Oecologica 19 pp. 367-375
2. Mocquard et al., 2001. Comptes Rendus de l’Académie des Sciences - Series III - Sciences de la Vie 324 pp. 701-707
3. Lawlor, 1976. Evolution 30 pp. 777-785