As a result of his stay in Europe, where he became acquainted with many of the principals in this great publication Biologia Centrali Americana, Calvert was invited to write the Odonata volume of the division of insects. He arranged to take specimens in lieu of other payment for his writing and thus greatly enlarged his personal cabinet, which was later bequeathed to the Academy of Natural Sciences. The correspondence about the conditions, is interfiled by author in Coll. 939. The notes are made in his autographed letterpress copy of the volume on Odonata above cited.