In each of the following passages,
a. What data are to be explained?
b. What hypotheses are proposed to explain them?
c. Evaluate the hypotheses in terms of the criteria presented in Section 13.3, pp. 564–566.

Swedish researchers, collaborating with colleagues in South Africa, found that dung beetles active during the day detect polarity patterns in sunlight and rely on those patterns to fi nd their way out of great masses of elephant dung. Dr. Marie Dacke, of the University of Lund, noticed subsequently that on moonlit nights one beetle species worked (rolling dung) particularly late. Could they have been relying upon the polarization of moonlight? Researchers set up polarizing filters to shift the moonbeams—and sure enough, the African beetle, Scarabaeus zambesianus , changed direction to compensate. When the polarization of the moonlight under the filter was rotated by 90 degrees, they found that beetles under that filter deviated from their course by almost exactly 90 degrees. “This is the fi rst proof,” writes Dr. Dacke in her report in Nature of 3 July 2003, “that any animal can use polarized moonlight for orientation.”