Diario de bullema

TL;DR: "Sapyga" louisi is not a true Sapyga and should instead be transferred to a new, yet to be described genus. Based on preliminary molecular analysis, its closest living relatives are species of the genus Eusapyga Cresson, 1880. Sapyga louisi is widely distributed in the Eastern USA and Canada and a related, undescribed species occurs in the Western USA.

The taxonomic status of Sapygidae in North America has been quite confusing, so it's important to understand the historical context first. Most of the Nearctic species were described by Ezra Townsend Cresson (1838–1926), who keyed the 21 species, including many new ones, in his 1880 publication and also described the new subgenus Eusapyga of Sapyga. Species were differentiated primarily based on coloration and no formal species descriptions were included. This makes it difficult to determine if the species described by him are all valid, especially since he didn't even list any type specimens. As such, the status of many species has remained unclear. The 'Catalog of Hymenoptera in America north of Mexico' published in 1979 lists 11 valid species in the genus Sapyga and 5 (including 2 additional subspecies) in the genus Eusapyga. Many of Cresson's species had been synonymized at this point, though I could not trace back the article(s) in which the species were formally synonymized.

Out of all Nearctic Sapyga species, Sapyga louisi was described relatively recently, by none other than the well known American entomologist Karl Vorse Krombein (1912–2005). He described the species very early in his career, in 1938, and at this point the internal taxonomy of the family Sapygidae was poorly resolved and many authors chose to recognize only two or three valid genera.

In the latter half of the 20th century, the Russian entomologist Nickolay Kurzenko made important contributions towards a clearer taxonomic image of the Sapygidae. He keyed the Eastern Palearctic species in 1986 and would go on to describe a new genus, Asmisapyga Kurzenko, 1994, from Turkey, in a publication co-authored by Austrian entomologist Josef Gusenleitner. He described another genus in 1996 while reviewing the Nearctic species, Krombeinopyga Kurzenko, 1996, named in honor of Karl Krombein, transferring two species previously included in Sapyga (S. aculeata Cresson, 1865 and S. pumila Cresson, 1880) to the new genus. He also received specimens of S. angustata Cresson, 1880, S. centrata Say, 1836, S. confluenta Cresson, 1880, S. martini Smith, 1855 and S. elegans Cresson, 1880, transferring the latter to the genus Polochrum Spinolia, 1805 and confirming the former 4 as true Sapyga. He notes that the generic placement of the 4 remaining species which he was unable to study could not be confirmed, including S. louisi.

Fortunately, Sapyga louisi is one of the most common and recognizable sapygid wasps of the new world. It is noticeably smaller than other Sapyga species and has much shorter antennae. The colour pattern, although variable, is characteristic: the mandibles are all black, the pronotum has an anterior yellow band (sometimes interrupted medically), the scutellum has a large, rectangular yellow spot and the second to fifth tergites have yellow markings, largest on T2 and sometimes with black 'eyespots'. An unusual feature of S. louisi is the position of the transverse carina of the frons. Instead of being widely separated from the upper margin of the clypeus like typical Sapyga and related genera, the carina touches the clypeus medially. This appears to be a plesiomorphic trait, to my knowledge first identified by Dutch entomologist Cees van Achterberg in his revision of the Oriental genus Parasapyga Turner, 1910, also present in Eusapyga and Huarpea Pate, 1947. Another critical distinction is the sexual modification of the male flagellum: in Sapyga (except subgenus Polosapyga Kurzenko, 1994), the terminal male flagellomere is strongly reduced in size, much smaller than the preapical flagellomere, an apomorphic condition also seen in Polochrum. In Sapyga louisi however, the terminal flagellomere is simple, about as large as the preceding flagellomere, and bears a linear tyloid which is absent in other Sapyga. Considering that the sexual modification of the male flagellum is an important diagnostic character for generic distinction in Sapygidae, it becomes increasingly obvious that S. louisi is not a true Sapyga. As kleptoparasites, host choice is another important generic feature, with many sapygid genera specialising on only one or two solitary bee genera. Sapyga generally parasitize bees in the genus Osmia, rarely Megachile, whereas S. louisi is a parasite of Heriades. Finally, the wing venation between S. louisi and other Sapyga differs significantly. In Sapyga, the outer wing vein of the third submarginal cell (2r-m) is strongly sinuous, resulting in a submarginal cell of strongly uneven length. In S. louisi, 2r-m is almost straight, resulting in a submarginal cell of more or less even length. Host choice and wing venation may show superficial resemblance to the Palearctic genus Sapygina Costa, 1887, however it's important to consider the state of the frontal carina, which has the pleisomorphic condition in S. louisi and the apomorphic condition in Sapygina. The structure of the ovipositor, an underexplored character which may hold significant phylogenetic value, is also very different in Sapygina. The similarities between Sapygina and S. louisi are therefore likely a result of convergent evolution.

So then what are the true affinities of Sapyga louisi? For one, it's morphologically quite similar to Eusapyga but is lacking in important diagnostic characters such as the reduced ocelli and tubercules on the frons and vertex. In my opinion, the species is best placed in a new genus. I ran a preliminary molecular phylogeny in MEGA 11 using public COI 5P barcodes accessible on BOLD Systems. Using maximum likelihood, a clade consisting of Eusapyga and Sapyga louisi along with two unidentified species received high (85%) bootstrap support. This clade was sister to all other sampled Sapygidae except Polochridium spinosum Yue, Li & Xu, 2017. These clades can be tentatively called "Eusapygini" (Eusapyga + Sapyga louisi and related species) and "Sapygini" (remaining Sapyginae, including Sapyga s.s.) and are characterized at least by the condition of the frontal carina.

Two unidentified lineages ("sp1" & "sp2") were recovered sister to Sapyga louisi, both represented by two sampled specimens. Sp1 is sister to sp2 + Sapyga louisi, collected in Costa Rica. The existence of this species is, as far as I understand it, long known, since it is mentioned in several papers, but it was never described. A specimen of this species is also present in the collection of the Natural History Museum in London. Sp2 is sister to Sapyga louisi, collected in California. This species has been actually observed on iNaturalist, often times misidentified as Sapyga louisi or Krombeinopyga pumila. Conveniently, both species seem to be largely allopatric, with Sapyga louisi being restricted to Eastern and Central USA and southeastern Canada, while sp2 occurs in (South)western USA.

While I have not seen any specimens of sp1 or sp2 in person, they seem to be quite different in coloration from Sapyga louisi and are thus easily distinguished. I have made a key based on coloration characteristics to identify members of the Sapyga louisi-clade:

1. Pronotum with a continuous pale band along anterior and posterior margin. Tibiae entirely dark, without pale markings. All tergites at least laterally with a pale marking. S2 with a very large pale spot, covering almost the entire surface of the sternite. Costa Rica —> sp1
   Pronotum with a medially interrupted, rarely continuous, pale band along anterior margin, posteriorly at most pronotal lobe pale spotted. Tibiae with a dorsobasal pale spot. T1 black, very rarely with pale markings. S2 black or with small anterolateral spots. USA and Canada, possibly also Mexico —> 2

2. Yellow markings more pale or ivory. Tibiae and tarsi dark, tibiae dorsobasally with a small or minute pale spot. Propodeum entirely dark or with small lateral spots. Metasomal markings usually more reduced, band of T2 sometimes interrupted medially. (South)western USA (CA, TX, CO) —> sp2
   Yellow markings more saturated yellow. Tibiae and tarsi reddish, tibiae dorsobasally with a large pale spot. Propodeum as a rule with posterolateral spots, sometimes small. Band of T2 large and rarely interrupted medially. Eastern and Central USA (VT, NY, MA, CT, PA, MD, OH, MI, IN, IL, NE, KS, TX), southeastern Canada (ON, QC) —> "Sapyga" louisi Krombein, 1938

References

• Cresson, E.T. (1880) Sapyga Latr. Proc. Month. Mtgs. Entomol. Sect. Acad. Nat. Sci. Philadelphia in Tr. Amer. Entomol. Soc. 8: xx–xxi.
• Krombein, K.V. (1938) Descriptions of Four New Wasps (Hymenoptera: Sapygidae, Sphecidae). Annals of the Entomological Society of America, 31(4), 467–470. doi: 10.1093/aesa/31.4.467
• Krombein, K.V., Hurd, P.D., Smith, D.R. & Burks, B.D. (1979) Catalog of hymenoptera in America north of Mexico. Washington, Smithsonian Institution Press. pp. 2735.
• Kurzenko, N.V. (1996) A new Nearctic genus of Sapygidae with a key to the Nearctic and Palearctic genera (Hymenoptera, Sapygidae). Memoirs of the entomological Society of Washington, 17, 89–94.
• Kurzenko, N.V. & Gusenleitner, J. (1994) Sapygidae from Turkey, with a key to palearctic species of Sapyginae (Hymenoptera). Linzer biologische Beitrage, 26(2), 583–632.
• van Achterberg, C. (2014) Revision of the genus Parasapyga Turner (Hymenoptera, Sapygidae), with the description of two new species. ZooKeys, 369, 61–77. doi: 10.3897/zookeys.369.6691
• Yue, Q., Li, Y-C & Xu, Z-F (2017) A remarkable new species of Polochridium Gussakovskij, 1932 (Hymenoptera: Sapygidae) from China. Zootaxa, 4227(1), 119–126. doi: 10.11646/zootaxa.4227.1.7

Example of sp1: https://www.inaturalist.org/observations/145240396
Example of sp2: https://www.inaturalist.org/observations/54361974

I'm delighted to share that my first paper has been published! We describe a new species of amisegine cuckoo wasp from the Arabian Peninsula, published in the Journal of Hymenoptera Research. This was quite a remarkable find, since chrysidids of the subfamily Amiseginae were not known from the northern Afrotropics and the new species represent the third species of the genus and first record of the subfamily from this region.

The Amiseginae are a rather peculiar group of cuckoo wasps. Rather than being kleptoparasites or parasitoids of other wasps and bees, they actively search for stick insect eggs in leaf litter. When an egg is found, the female pierces the shell with her pointed mandibles and lays an egg of her own inside of it, after which the larva will feed on the yolk of the phasmid egg. They are in this regard similar to the even more morphologically aberrant Loboscelidiinae.
Even among members of the subfamily, Anachrysis is a real standout. Most other Afrotropical Amiseginae are quite strongly brachypterous, with males and females flightless. They are usually blackish or brownish in color, though some species (Alieniscus) have a reddish mesosoma. Anachrysis however has both sexes fully winged and exhibits extensive metallic blue integument. Based on several morphological features, such as the odd flattened mandible and translucent lateral lobes of the clypeus of the male, short metanotum without median enclosure and rounded propodeum, their closest relatives are probably the Nearctic and Neotropical Adelphe.

If you are interested in reading the publication, it is available here: https://doi.org/10.3897/jhr.96.107489