Jennifer Maigret
The genus Histiogaster contains a number of species associated with subcortical habitats and fungal fruiting bodies. Okabe (1993) first reported on the biology of an unidentified species of Histiogaster collected from the fungus, Trichoderma harzianum, an important pathogen in commercial mushroom production in Japan. Comparison of this mite with specimens identified as Histiogaster arborsignis from northern Michigan (OConnor, 1990) yielded no morphological differences. However comparison of these specimens with specimens of H. arborsignis collected in Arkansas from the typical habitat association (galleries of the southern pine beetle, Dendroctonus frontalis) provided by Dr. John Moser of the USDA,Forest Service, did yield one consistent morphological difference in the females. In an attempt to test reproductive compatability among these populations, we have maintained live cultures of populations originating in Japan, northern Michigan and Arkansas. Breeding experiments completed to date indicate that the Japanese and Michigan populations are completely interfertile, whereas the Japanese and Arkansas populations are reproductively isolated (the Michigan X Arkansas cross has not been completed as yet). This, plus the minor morphological difference, suggests that sibling species are involved, and a description of the northern species is in preparation.
Histiogaster sp. near arborsignis, deutonymph and male. Note pigmented ocelli in the deutonymph and posterior, fan-like setae in the male, both characteristic of the genus Histiogaster.