"Originally these deities seem to have been personifications of the vapours which are attracted by the sun, and form into mist or clouds: their character may be thus interpreted in the few hymns of the Rigveda where mention is made of them. At a subsequent period when the Gandharva of the Rigveda who personifies there especially the Fire of the Sun, expanded into the Fire of Lightning, the rays of the moon and other attributes of the elementary life of heaven as well as into pious acts referring to it, the Apsarasas become divinities which represent phenomena or objects both of a physical and ethical kind closely associated with that life; thus in the Yajurveda Sunbeams are called the Apsarasas associated with the Gandharva who is the Sun; Plants are termed the Apsarasas connected with the Gandharva Fire: Constellations are the Apsarasas of the Gandharva Moon: Waters the Apsarasas of the Gandharva Wind, etc. etc.… In the last Mythological epoch when the Gandharvas have saved from their elementary nature merely so much as to be musicians in the paradise of Indra, the Apsarasas appear among other subordinate deities which share in the merry life of Indra's heaven, as the wives of the Gandharvas, but more especially as wives of a licentious sort, and they are promised therefore, too, as a reward to heroes fallen in battle when they are received in the paradise of Indra; and while, in the Rigveda, they assist Soma to pour down his floods, they descend in the epic literature on earth merely to shake the virtue of penitent Sages and to deprive them of the power they would otherwise have acquired through unbroken austerities."--GOLDSTÜCKER'S Sanskrit Dictionary.