Horismenus fraternus

Differs from congeners by subtle morphological features of the antennae and propodeal sculpture; exact diagnostic characters require microscopic examination and reference to original species description. Distinguished from other eulophid genera by the combination of reduced wing venation, number of antennal segments, and structure of the mesosoma. Similar to other small green eulophids such as species of Chrysocharis and Closterocerus, but Horismenus lacks the distinct notauli and has a different arrangement of setae on the mesoscutum.

Small wasp, body length approximately 1-2 mm. Members of Horismenus exhibit reduced wing venation characteristic of Eulophidae, with forewings showing a single reduced submarginal vein and lacking a distinct marginal vein. Body typically metallic green or blue-green. Antennae short, with 3-4 anellate segments and compact funicle. Mesosoma compact; propodeum with distinct plicae. Gaster sessile or subsessile, often appearing laterally compressed.

Recorded from eastern Canada: Ontario and Quebec. No additional distribution records available.

Presumed parasitoid based on family-level biology; specific host relationships and ecological function undocumented.

• Chrysocharis spp.Similar small metallic green eulophids with reduced wing venation; distinguished by presence of distinct notauli and different antennal segmentation in Chrysocharis.
• Closterocerus spp.Overlapping size range and coloration; Closterocerus species typically show different propodeal structure and forewing setation patterns.
• Other Horismenus speciesRequire detailed examination of antennal proportions, propodeal plicae arrangement, and gaster sculpture for separation; many species poorly differentiated in literature.

• parasitoid
• chalcid wasp
• North America
• Eulophidae
• Horismenus

• BugGuide
• GBIF taxonomy match