Sentence:  Earless ghost swift moths become “invisible” to echolocating bats by forming mating clusters close (<WSD>less</WSD> than half a meter) above vegetation and effectively blending into the clutter of echoes that the bat receives from the leaves and stems around them. 
Meaning of the word marked with <WSD> tags:  (little): a smaller amount (of); not as much. (from 14th c.)