Sympatry was noted with Hystrichopsylla dippiei Rothschild and H. occidentalis sylvaticus Campos & Stark and earlier in New Mexico with Peromyscopsylla selenis (Rothschild) and P. hamifer vigens (Jordan), 1970s. Most significant was the recent occurrence of H. dippiei larvae and H. o. sylvaticus adults in the same nest of a red squirrel, Tamiascirus hudsonicus (Erxleben) RN-131 in the San Francisco Mountains, Catron County, Mogollon Volcanic Plateau, 23 October 1995. Collections on 20 August 1993, 20 September and 23 October 1995, 1 October 1998, and 1 and 4 October 1999 recorded nine nests of red squirrels and two nests of Mexican woodrats, Neotoma mexicana Baird, the latter with visits by deer mice, Peromyscus maniculatus (Wagner) or P. gratus Merriam. Red squirrel nests had one to four species of adult fleas including one of a woodrat. Adult species totaled six: H. o. sylvaticus, Catallagia decipiens Rothschild, Anomiopsyllus nudatus (Baker), Megarthroglossus aff. bisetis Jordan & Rothschild, Orchopeas caedens (Jordan), Orchopeas neotomae Augustson. Mexican woodrat nests had six and seven species of adult fleas including mouse and red squirrel species. Adults totaled nine: H. o. sylvaticus, C. decipiens, A. nudatus, M. aff. bisetis, Aetheca wagneri (Baker), Malaraeus telchinus (Rothschild), O. caedens, O. neotomae, and Plusaetis sibynus (Jordan).