Graduate Thesis Or Dissertation
 

Systematics and host associations of Ormyrus species (Hymenoptera: Chalcidoidea)

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  • The genus Ormyrus has a worldwide distribution and comprises about sixty recognized species. The higher taxonomic relationships of the genus are uncertain, as evidenced by its placement in the families Ormyridae, Pteromalidae, or Torymidae. Here, the genus is described in detail and a preliminary catalog of the world species is provided. The Nearctic species of Ormyrus have never been revised and the original descriptions are inadequate for separating species. Fifteen species have been described from the Nearctic, but two were previously synonymized. After examining all type material and over 8000 additional specimens, I consider nine species to be valid and relegate five to junior synonymy. The nine recognized species are redescribed. With the description of seven new species, the genus now comprises sixteen Nearctic species; a key is provided for separating these species. Certain characters such as color and size were found to be quite variable in some species. Surface sculpture, as documented through the use of SEM, proved especially useful in separating species. Thirteen of the sixteen Nearctic species may be associated exclusively with cynipid galls on oaks. Host records from specimen labels are summarized in tables, one of which includes an updated list of all Nearctic oak cynipids. Twig galls harbor several oligophagous species of Ormyrus, many leaf galls just a single polyphagous species, and "apple" galls usually none. Other hosts of Nearctic species include cynipid galls on Rosaceae and a pteromalid gall on blueberry. In other parts of the world, dipteran and chalcidoid galls may be important hosts. Distributional patterns of Nearctic Ormyrus species are compared with those of host cynipids and oaks.
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