Lousewort was a low-ranking rat in the Rapscallion army who was friends with another rat, Sneezewort. The pair were incredibly stupid, often showing their lack of intelligence. Lousewort was even stupider than Sneezewort, and was often taken advantage of.
Lousewort wanted to salvage a ship's wheel from the scuttled Rapscallion fleet, but was ridiculed by Sneezewort and the wheel was thrown away. Unfortunately, it hit the weasel Hogspit, and turned him into an enemy of the rats.
Along with Hogspit, Lousewort was promoted to the rank of Rapscour after the previous Rapscours, Borumm and Vendace, were declared traitors. On a scouting expedition, Hogspit was killed by Log-a-Log and Lousewort and the surviving scouts were punished by being forced to stand in a river all night. Borumm and Vendace escaped with the scouts, but killed the stoat Lugworm. Lousewort was shocked by this action and was knocked out by Borumm for his trouble. After regaining his senses, he alerted Damug Warfang of the rebels' escape. Although Damug noted that Lousewort was stupid, he told him that he was at least a loyal soldier and demoted him back into a common soldier, ending his punishment.
Later, Lousewort and his friend Sneezewort were instructed to keep watch over Miggo and Burfal (who were actually Long Patrol hares Tamello De Fformelo Tussock and Midge Manycoats). While Sneezewort was gathering firewood, Lousewort was knocked out by the hares and woke up later to find they had escaped. Following the advice of the ferret Rinkul, the two rats deserted the Rapscallions. Their fate is unknown.
Lousewort and his friend, Sneezewort, can be interpreted as two innocents swept up in the dramatic events that comprise The Long Patrol; they are often taken advantage of by other creatures, and really do not seem to be that evil, as they show remorse shortly after the execution of Borumm and Vendace.