His first work on cecidology dated back to 1897 (when he was 21 yrs old) and he reported 124 galls of which 21 were caused by eriophyid mites. Trotter travelled around Italy between 1899 and 1909 and described 742 galls in 20 papers. At the age of 28 he founded a journal called Marcella in honour of Marcello Malphigi which dealt with cecidology. He later became professor of plant pathology at the University of Naples and wrote more than 400 publications with nearly 110 on plant galls. He described several new species of Cynipidae and Cecidomyiidae some with Jean-Jacques Kieffer.