As entomologist, professor and editor, Calvert corresponded with thousands of colleagues, students and authors. His mailing list of the recipients of his separates numbered 557, while his correspondence was maintained with 1,010 persons. Some hundreds of his own queries as well as answers to letters from others, were copied in longhand, although in later years much is in typescript. These answers and queries are retained with the letters concerned, but no exact record of their numbers was made. Most of this correspondence deals with Odonata and his researches connected with that group. Another large group of letters, written as editor of Entomological News may be found in Coll. 492.