Chasca gravis Musetti & Johnson, new species
Creators: name: Johnson, Norman F.
name: Musetti, Luciana
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Hexapoda
Hymenoptera
Monomachidae
Chasca
Chasca gravis

description: Chasca gravis Musetti & Johnson, new species
urn:lsid:zoobank.org:act:D9D54C0F-0E42-4CF3-9A07-3067C115B25A urn:lsid:biosci.ohio-state.edu:osuc_concepts:276542 Figures 10–15; Morphbank11
Description. Body length of female: 7.8 mm (n=1). Body length of male: 5.6–7.5 mm (n=12). Fore wing length of male: 4.5–5.8 mm (n=12). Body color of female: dark brown throughout. Sculpture of female vertex: smooth. Frontoclypeal suture of female: weakly indicated, nearly obsolete. Ventral margin of clypeus: sinuate, longest medially. Tyloid of male antenna: forming raised keel, highest apically (Fig. 15). Sculpture of female pronotum: smooth (Fig. 11). Length of notaulus: abbreviated posteriorly, distinctly separated from transscutal articulation (Fig. 11). Posterior separation of notauli: distinctly separated by distance subequal to 3x width of notaulus. Shape of mesoscutellar pit: transversely oval. Sculpture of female mesopleural depression: smooth (Fig. 12). Length of female fore wing: short, but distinct, extending posteriorly to propodeum (Figs. 10–12). Length of female hind wing: short, but distinct, extending posteriorly to propodeum.
Diagnosis. The female of Chasca gravis may be distinguished by the short, but clearly developed wings extending posteriorly to the propodeum, the dark brown color of the body, and the smooth vertex and pronotum. Males may be recognized by the strongly raised, knifelike tyloids on the basal flagellomeres.
Etymology. The adjective gravis, meaning heavy in Latin, refers to the generally robust habitus of the female of this species.
Link to Distribution Map. [http://hol.osu.edu/map-full.html?id=276542]
Material Examined. Holotype, female: PERU: Cuzco, Urubamba, 7.II–9.II.1968, A. Garcia & C. Porter, OSUC 19234 (deposited in MCZC). Paratypes: PERU: 346 males, OSUC 116694 (AEIC); OSUC 117107, 19235– 19477, 19479, 19486–19513, 19517–19578 (MCZC); OSUC 19478, 19480–19485, 19514–19516 (OSUC).
http://www.morphbank.net/?id=579882 Comments. This species is only recorded so far from the region around Cuzco, Peru at an elevation of more than 3000 m. Only a single female is known, but, in contrast, over 300 males have been collected. The difference is undoubtedly due to the different biological imperatives of the two sexes, the males searching widely for females, and the females searching for hosts, probably in the litter or soil.
Biogeography of Monomachidae. Interpretation of Fig. 1 in the context of the biogeographic history of the family must be tempered by acknowledging the weakness of the available anatomical characters for inferring phylogenetic relationships. However, Chasca consistently emerges as the most basal clade followed by the the Australian/New Guinea species, and these followed by the flowering of Neotropical Monomachus. It is tempting to interpret this as a transantarctic distribution generated by vicariance of the southern continents. However, C. gravis is found well north of the Atacama Desert, and M. porteri is widespread in Chile, both facts muddying that simple hypothesis. An alternative hypothesis, that the current biogeographic pattern represents an ancestral widespread distribution disrupted by subsequent extinction may appear less parsimonious, but should not be rejected out of hand because there are many examples of putatively “southern” taxa that also occur as inclusions in Baltic amber e.g., the proctotrupoid genus Peradenia (Johnson et al. 2001). The vicariance hypothesis could be strengthened by additional evidence supporting the monophyly of the Australia /New Guinea species, most likely using sequence data.
description: Published as part of Johnson, Norman F. & Musetti, Luciana, 2012, Genera of the parasitoid wasp family Monomachidae (Hymenoptera: Diaprioidea), pp. 31-41 in Zootaxa 3188 on pages 37-38, DOI: 10.5281/zenodo.211047