Diagnosis. It belongs to the annulicornis species-group, and can be separated from other species within that group based on the combination of T2 mostly smooth and polished, antenna brown with flagellomeres 6–8 white (rarely also posterior half of flagellomere 5, white band clearly occupying less than one third of antenna length), and metasoma with T3+ partially brown. Those features are shared with the morphologically similar P. margaritapenonae, but P. luisguillermosolisi has the mesosoma entirely orange-yellow (while margaritapenonae has darker areas on propodeum, metapleuron, metascutellum and axillar complex).
Description. Female. Body length 2.4–2.5 mm. Fore wing length 2.6–2.7 mm. Head color: mostly dark brown to black; except for orange on most of frons and face, and yellow clypeus, labrum, mandibles, and spot on lower corner of gena near oral foramen. Flagellomere color: central flagellomere white-yellow, rest dark brown to black. Mesosoma color: entirely orange to yellow-orange. Metasoma color (dorsally): mediotergites 1–2 orange-yellow, rest of mediotergites brown. Coxae color: all pale. Metatibia color: pale. Metatarsus color: pale. Pterostigma color: mostly dark, but with anterior pale spot. Mediotergite 1 length/width at posterior margin 4.1–4.5 ×. Mediotergite 1 maximum width/width at posterior margin 2.3–2.4 ×. Mediotergite 2 width at posterior margin/length: 4.0–4.1 ×. Mediotergite 2 sculpture: Mostly smoth and polished. Ovipositor sheaths length: 0.7 × as long as metatibia. Male. The only known specimen is missing its head, but the coloration of mesosoma and metasoma is darker than the female holotype. Pseudapanteles luisguillermosolisi is morphologically similar to P. margaritapenonae, but the mesosoma is entirely orange yellow in the former compared to orange yellow but with darker areas on the propodeum, metapleuron, metascutellum and axillar complex in the latter. Also, these species are at least 25 base pairs different (4%) in the DNA barcoding region.