Come and Gone: Description of a New Species of Eucharitidae (Hymenoptera) Attacking Solenopsis (Hymenoptera: Formicidae) in Texas

Eucharitidae (Hymenoptera: Chalcidoidea) are the only family in which all members are specialized parasitoids of ant brood, with species of Orasema Cameron (Oraseminae) parasitizing several genera of Myrmicinae, including Solenopsis Westwood and Pheidole Westwood (Formicidae). In 1988, a new species of Orasema was discovered in southern Texas attacking the brood of what is recognized as a Solenopsis geminata (Fabricius) (Hymenoptera: Formicidae) × Solenopsis xyloni McCook (Hymenoptera: Formicidae) hybrid. Adults of Orasema oviposit onto the green stems and leaves of Vachellia sp. (Fabaceae). Orasema taii n. sp. was only found attacking the hybrid colonies and was not recovered from adjacent nests of Solenopsis invicta Buren (Hymenoptera: Formicidae), which at that time were equally abundant in the area. Wasps were abundant at the time of collection, but since these initial collections, the parasitoids have not been recovered. Hybrid populations have declined precipitously with the invasion of the imported fire ant, and both the hybrid and parasitoid may have been extirpated at least from the area of discovery. Based on morphological and molecular evidence, O. taii n. sp. is placed into the Orasema bakeri species group. The adult and immature stages and their behavior in the field are described.