Diachasma ferrugineum (Gahan, 1915)

Although currently placed in the genus Diachasma because of the shortened clypeus, Diachasma ferrugineum and two closely related species, Diachasma alloeum (Gahan) and Diachasma muliebre (Muesebeck), share many morphological and biological similarities with the New World species of the genus Diachasmimorpha (Wharton 1997).

Figures of the closely related D. alloeum, as well as additional comments, can be found under the Diachasma page.

Taxonomic History / Nomenclature
This species was originally described in the genus Opius.
Diagnosis and Relationships
A key for distinguishing the three North American species of Diachasma that have been reared from Tephritidae is provided by Wharton and Marsh (1978).

This species is nearly identical to Diachasma muliebre, but the sculpture of the petiole differs slightly (Muesebeck 1956). The West Coast species (muliebre) is thought to be thelytokous whereas ferrugineum is arrhenotokous, with normal production of males and females.

The ovipositor is distinctly longer than the body in Diachasma alloeum, and about equal in length to the body in ferrugineum and muliebre. However, this character needs to be more critically examined because of potential allometry problems associated with hosts (and resulting parasitoids) that vary considerably in size.

D. ferrugineum has been found in northeastern United States, eastern Canada, and Florida. It has been released and apparently recovered in California, but establishment needs confirmation. See discussion and additional references in Wharton and Marsh 1978.
Biology / Hosts
Normally attacking the cherry-infesting flies Rhagoletis cingulata (Loew) and R. fausta (Osten Sacken), and only rarely attacking the apple maggot, R. pomonella (Walsh).