Robert McLachlan’s nomination certificate of 1874 was recorded in the minutes of an ordinary meeting of the Royal Society of London held on 29 January 1874; CD was listed as having signed ‘from general knowledge’. The certificate itself has not been found. A later certificate dated 10 February 1876, also signed by CD but this time ‘from personal knowledge’, is in the archives of the Royal Society (Royal Society, GB 117, EC/1877/11). McLachlan was elected as a fellow on 7 June 1877.

McLachlan had been a member of the Entomological Society of London since 1858, and served as treasurer for the society between 1873 and 1875. He was also the first editor of the Entomologist’s Monthly Magazine (ODNB).