龍鼓灘山谷有着豐富的蝴蝶物種多樣性（超過130個品種），因此被廣泛認為是香港最重要的蝴蝶棲息地之一。於香港，這裡擁有數量最多的稀有蝴蝶－－紅鋸蛺蝶。其他在此處記錄到而具保育價值的物種包括：史氏絹斑蝶、尖翅弄蝶及緯帶趾弄蝶。龍鼓灘山谷的風水林和天然林地都是蝴蝶重要的繁殖地，一些稀有的寄主植物在此處都有記錄，如蛇王藤等。蛇王藤在香港只有在少數地方有記錄，亦是紅鋸蛺蝶唯一已知的寄主植物。

The Site is widely reconized as one of the most important butterfly habitats in Hong Kong with a high diversity of butterfly species recorded (over 130 species). The Site supports the largest population of the rare butterfly species Cethosia bibles (紅鋸蛺蝶) in Hong Kong. Other butterfly species of conservstion value recorded at the Site include Parantica swinhoei (史氏絹斑蝶), Badamia exclamationis (尖翅弄蝶) and Hasora vitta (緯帶趾弄蝶).
The Fung Shui wood and natural woodland at the Site are important breeding habitats of butterflies, where a diverse assemblage of butterfly larval food plants has been recorded, including the rare vine Passiflora moluccana var. teysmanniana (蛇王藤, King Snake Creeper). In Hong Kong, P. moluccana is the only known larval food plant of C. bibles and is only recorded at a few other localities.