pheromone extract from a single gland

例句：

1. 1.Pheromones are chemicals that animals use to communicate with each other.
   信息素是动物用来彼此沟通的化学物质。
2. 2. The study of pheromones has led to new understanding of animal behavior.
   对信息素的研究已经揭示了动物行为的新理解。
3. 3.Insects emit pheromones to attract mates and defend their territories.
   昆虫通过释放信息素来吸引配偶和保卫领土。