light infantry

noun2

1. •
   Ground combat soldiers who are not mechanized, and whose role is to harass the enemy in front of the main body of infantry.
2. •
   (slang, no longer used) Bedbugs or fleas.

   • The affair began by a skirmishing of the fleas, who acted as cavalry; then came the main body of lice, followed by the light infantry of bedbugs, to the number of forty thousand. — 1906