[Thracian:] And I asked him whether daemons were endowed with affectivity (ἐμπαθεῖς). “Yes, indeed,” he said, “just as some of them even discharge sperm and breed worms from that sperm.” But it is incredible that daemons should be capable of secretion (περίττωσιν) or possess animal-like genital organs, said I. “They do not possess organs,” he said. “They are, however, capable of secretion, on this point you may believe me.” But surely they must feed the same as we do, said I. “Some are nourished by indrawn breath (δι’ ἐισπνοῆς),” he said, “like breath (πνεῦμα) in the bronchial tubes and the sinews, and some by moisture, feeding not through a mouth, as we do, but in the manner of a sponge or a shellfish, absorbing the external moisture surrounding them and then expelling a spermatic accretion. Not all demons are capable of this, however, but only those species that are conjoined to solid matter, those that shun the light, and those that dwell in water or underground.”
Michael Psellus, Dialogus de Daemonum Energeia seu Operatione (PG 122: 840c-841a)
trans. Alistair Ian Blyth