A new species of Tanaostigmodes from the emarginatus species group (Hymenoptera: Chalcidoidea: Tanaostigmatidae) gall forming on Handroanthus pulcherrimus (Bignoniaceae) in Buenos Aires, Argentina

Abstract

A new gall-inducing species of Tanaostigmodes Ashmead, 1896 (Hymenoptera: Chalcidoidea: Tanaostigmatidae) is described from Handroanthus pulcherrimus (Bignoniaceae) in Buenos Aires Province, Argentina. The new species, Tanaostigmodes lapachosus sp. n., belongs to the emarginatus species group. Specimens were collected from galls on the midrib and petiolules of leaflets of H. pulcherrimus, a native tree widely distributed in northeastern Argentina, Paraguay, and Brazil, and commonly known as “lapacho amarillo misionero”. A survey conducted at the Arturo E. Ragonese Botanical Garden (INTA) revealed galls in 85% of the sampled trees, with an average of 34.7% of leaflets per leaf affected. The galls are ovoid, bump-shaped, and occur in both seedlings and mature trees. Morphological examination of adults was carried out using stereomicroscopy, slide mounting, and digital imaging. The discovery of T. lapachosus sp. n. highlights the importance of taxonomic surveys in less-studied ecosystems and contributes to the understanding of plant–insect interactions in South America. The high incidence of gall formation raises important questions about its impact on host tree health, with potential implications for future management of H. pulcherrimus in natural and urban environments. Detailed morphological descriptions, illustrations, and a key to distinguish this species from all members of the species group are provided.