Writings by Abbott Handerson Thayer, primarily on the topic of concealing coloration and his observations of nature, include four small notebooks. His notes and draft essays, often written on small scraps of paper or the back of other documents, are on the topic of concealing coloration in nature, and the related topics, the invisibility of icebergs and the concealing coloration in military uniforms and warships. Many of his notes appear to be preparations for lectures or letters to the editor on these topics, or responses to the negative feedback from his book , published in 1909. Also found are draft essays on the restoration of works of art and notes and essays on various subjects such as the Boer war, art, and other thoughts on nature.

This subseries contains writings by the Thayer family and writings by scholars, primarily about Abbott Handerson Thayer. Included are writings by Emma Thayer, such as a manuscript for a story entitiled "Ernest" and two poems, and Mary Thayer's diary and corresponding hand-made calendar, written when she was ten years old. Writings by Gladys Thayer Reasoner include a brief biographical sketch of her father, a biography of her son, Allen Reasoner, who died in 1943 in a plane crash, and stories and other writings she wrote as a young girl.

Writings by others about Abbott Thayer include a draft manuscript by Nancy Bell, wife of artist Arthur Bell, about Thayer's book on concealing coloration. This series also contains writings by unidentified authors, such as draft writings about George Gray Barnard, possibly written by David or Gladys Thayer Reasoner, and miscellaneous writings and poetry by others. Folders are arranged by author and title of work, if known, and chronologically within each folder.