The Aix-la-Chapelle “shower of blood,” July 1608

Report. At the beginning of July 1608, a supposed shower of blood was reported for several miles around the suburbs of Aix-la-Chapelle. Blood-coloured drops stained the walls of nearby villages, stones in the highways, and fields, while very large numbers of butterflies were present. The drops were not found in the city centre or in places the butterflies did not reach.

The proposed mechanism

Explanation. M. de Peiresc traced the stains to large drops of blood-coloured liquid exuded as large chrysalides transformed into butterflies. Gibb presents this as a natural explanation of what observers saw, not as a reason to dismiss or mock their testimony. He adds that Peiresc’s explanation was, in his view, very likely applicable to some older reports of “showers of blood” that occurred during warm seasons when butterflies were numerous, including reports associated with Gregory of Tours.

What remains uncertain

Uncertainty. The Aix-la-Chapelle account supports Peiresc’s explanation because the stains, their distribution, and the abundance of butterflies coincided. Gibb connects the mechanism to some older reports, but the passage does not claim that it explains every historical account of red rain or every event described as a shower of blood. The historical report and its proposed explanation should therefore be kept distinct: the observers reported red drops and butterflies, while Peiresc and Gibb supplied a possible cause.