Sentence:  Earless ghost swift moths become “invisible” to echolocating bats by forming mating clusters close...above vegetation and effectively <WSD>blending</WSD> into the clutter of echoes that the bat receives from the leaves and stems around them. Many insects probably use this strategy, which is a close analogy to crypsis in the visible world—camouflage and other methods for <WSD>blending</WSD> into one's visual background. 
Meaning of the word marked with <WSD> tags:  To be mingled or mixed.