*patagium*

‖n.; pl. Patagia [ L., an edge or border. ] 1. (Anat.) In bats, an expansion of the integument uniting the fore limb with the body and extending between the elongated fingers to form the wing; in birds, the similar fold of integument uniting the fore limb with the body. [ 1913 Webster ]

2. (Zool.) One of a pair of small vesicular organs situated at the bases of the anterior wings of lepidopterous insects. See Illust. of Butterfly. [ 1913 Webster ]