His father, William, was a physician turned farmer and general merchandiser, and his mother, Nancy, was the daughter of a reverend.

Scientists in 1970–1972 did a similar survey, and found that most of the bees noted by Robertson were still present.

This is presumably due to the existence of bee habitat in hedgerows, on slopes, and in other non-agricultural land in the survey area.

Study was published in Science, February 2013, Plant-Pollinator Interactions over 120 Years: Loss of Species, Co-Occurrence and Function by Laura A. Burkle1, John C. Marlin, Tiffany M.

[5] ITIS records citing taxon author "Robertson, 1903" [3] 1896: Notes on bees of the genus Prosopis[4]