The Jensen Psyllid Collection comprises approximately 22,000 specimens. Specimens from western North America make up the majority of the material. However, an identified, European collection is maintained as well. Approximately two-thirds of the specimens are preserved in alcohol. The collection also includes approximately 800 slides and some 6000 pinned specimens.
All specimens bear lot numbers which reference field notes and additional data in a card file.
Alcohol and slide material is maintained separately, while Jensen integrated his dried material with that of the rest of the collection. The collection contains numerous paratypes, while Jensen's holotypes have been placed on loan of indefinite duration at the California Academy of Sciences. Dr. Jensen also amassed a large collection of reprints dealing with the systematics and biology of psyllids which is now part of the Essig Museum reprint collection. The Psyllidae of California. Ph.D. Dissertation, University of California.