Horismenus Walker is one of the largest genera of Eulophidae with 414 known species, of which most were only recently described (Hansson 2009; Hansson et al. 2011; Narendran et al. 2011; Hansson et al. 2014; Pikart et al. 2015). The genus occurs almost exclusively in the New World, except for Horismenus absonus Narendran & Girish Kumar (India) and Horismenus specularis (Erdös) (Europe) (Hansson 2009; Narendran et al. 2011). Horismenus species are endoparasitoids with host records known for 25% of the species, which include eggs and larvae of several families of Coleoptera, Diptera, Hymenoptera, Lepidoptera, Mantodea, Neuroptera and Orthoptera, and eggs/egg sacs of spiders (Hansson 2009; Hansson et al. 2011; Hansson et al. 2014).
Horismenus is one of the most commonly collected groups of eulophids in tropical America (Hansson 2009) and also one of the most characteristic, being easily recognized and separated from other genera by the following features: pronotal carina present; scuto-scutellar suture with a fovea; scutellum usually with a median groove and with lateral mesh-rows; propodeum with anterolateral foveae, median carina, submedian grooves and plicae. Hansson (2009) recently revised the genus and provided a key for species identification.