Fleas and flies
(Other definitions for pests that I've seen before include "Steps taken about nuisances" , "Take steps to troublesome animal." , "Persistently annoying persons" , "Steps (anag.)" .)
(Other definitions for insects that I've seen before include "Small arthropods" , "Six-leggged creatures" , "Tiny creatures" , "Considerable class" , "Small invertebrate creatures" .)