Only males have scent scales. The pheromones attract females of that species. Their flowers are used in reproduction. Angiosperms evolved 125 million years ago and became the dominant plants about 100 million years ago. Antennae are used for the sense of smell and balance.
Butterflies have two segmented antennae with a small club at the end of each.
Moths have antennae without the club. The flowers are used in reproduction. They evolved during the Cretaceous period . Butterflies and moths are important pollinators of these plants. An army is a group of caterpillars.