Beltane is a festival that marks the return of summer with the lighting of fires; where people could burn their winter bedding and floor coverings, ready to be replaced afresh. Referred to as a Gaelic ceremony, it has been celebrated for thousands of years throughout the United Kingdom and Europe. In fact in Ireland, it supposedly marks the arrival of the Gaels on to Irish shores.
Also referred to as Roodmas, Rood day, the Eve of St Walburga's Day and Walpugis Nacht (these last two show relations with St Walburga, who was born in Sussex and died in AD180 after emigrating to Germany. Walburg is also an old Teutonic name for the Earth Mother), this date also marks the festivals of Hades or Pluto, God of the Underworld.
Early accounts of Beltane celebrations have been passed down by Julius Caesar, whose description of the Scottish Celts celebrations of the festival must be seen as biased.
Supposedly, animal sacrifices would be made each Beltane to ensure the fertility of their crops, however, every five years the Highland Celts would sacrifice humans, the numbers being made up of convicted criminals and prisoners of war. They would be sacrificed by the Druids, though the manner of their death would vary. Many were supposedly shot with arrows, but descriptions of Gaulish Celt ceremonies have them being burnt alive in huge wicker men.
While their is little evidence to suggest the use of the wicker man, many Iron Age 'bog bodies' have been found preserved in peat in the British Isles and Northern Europe. These show signs of having been ritually murdered in a variety of ways (strangulation, blows to the head, throat cutting and a combination of each). While this does not suggest they were sacrificed on Beltane, it does give a glimpse into the savage part of ancient religion.
Fires were lit on hilltops at Beltane as late as the 1700s, and Beltane is still a major ceremonial date in the Wiccan and Pagan year, although these don't include sacrifices.
Later accounts of Beltane festivities refer to a Beltane Cake, baked with eggs. A special piece of this referred to as the Beltane Carline spelt symbolic doom to whoever was unlucky enough to receive it. Once identified, the person with the Beltane Carline would be set upon by some of the others who would attempt to throw them on the fire. This would be prevented by the rest of the festivalgoers. The unlucky person would then be considered a symbolic sacrifice and referred as being dead for the rest of the evening.
SOURCES:
Golden Bough - Frazer
What Witches Do - Stewart Farrar
Celtic gods and Goddesses - R J Stewart.