What was meant by the charge: "the upsetting of the lamp"?

In Justin Martyr's First Apology Chapter 26, we read: > And whether they perpetrate those fabulous and shameful deeds — the upsetting of the lamp, and promiscuous intercourse, and eating human flesh — we know not; but we do know that they are neither persecuted nor put to death by you, at least on account of their opinions. The context is: >...the devils put forward certain men who said that they themselves were gods; and they were not only not persecuted by you, but even deemed worthy of honours. But these three accusations seemed to have been laid against the Christians, charges which Justin supposed was rather invented by them that probably committed it themselves and then charged to the Christians: "upsetting of the lamp, and promiscuous intercourse, and eating human flesh". The "promiscuous intercourse" evidently referred to incestuous practices and "eating human flesh" to cannibalism which Eusebius confirms were charges laid against Christians,... > And some of our heathen servants also were seized, as the governor had commanded that all of us should be examined publicly. These, being ensnared by Satan, and fearing for themselves the tortures which they beheld the saints endure, and being also urged on by the soldiers, accused us falsely of **Thyestean banquets** and **Œdipodean intercourse**, and of deeds which are not only unlawful for us to speak of or to think, but which we cannot believe were ever done by men. *Ecclesiastical History, V.1.14* Other non-Christian writers also refer to such accusations against the Christians that explains two of these charges in *The First Apology* , but I cannot find a meaningful explanation of what "upsetting of the lamp" means.