But Areus, by setting frequent ambushes and occupying the most difficult points on the march, kept cutting off the Gauls and Molossians who brought up the rear for Pyrrhus.
Edition :
Plutarch Lives IX: Demetrius and Antony, Pyrrhus and Caius Marius, Ed. Jeffrey Henderson, trans. Bernadotte Perrin (The Loeb Classical Library 101), Harvard University Press: Cambridge/MA - London 1968 (first ed. 1920).
Remark :
thirdperson: Pyrrhus sends his son Ptolemaeus to relieve the rearguard. This is mentioned in 30.3. date: The date is taken from the New Pauly.
http://referenceworks.brillonline.com/entries/brill-s-new-pauly/pyrrhus-e1015710 long-term consequence: Pyrrhus' son Ptolemaeus dies while trying to relieve the rearguard. This is mentioned in 30.4.