Messapus Simon, 1898

Haddad, Charles R. & Mbo, Zingisile, 2015, Five new species of the Afrotropical dark sac spider genus Messapus Simon, 1898 (Araneae: Corinnidae), Zootaxa 4057 (3), pp. 385-398 : 387-389

Genus Messapus Simon, 1898

Messapus Simon, 1898: 214 ; Reiskind, 1969: 166; Bosselaers & Jocqué, 2000: 307; Haddad, 2013: 16 . Type species: Messapus martini Simon, 1898 , by original designation.

Remarks and supplementary descriptive data: Haddad (2013) provided a detailed description and diagnosis for the genus. The presence of a lobe found on the distal side of the cheliceral paturon in front of the fang base (cheliceral promarginal pronounced mound, CPPM, Fig. 3 ; also see Ramírez 2014: 53) is a structure reported from the genus for the first time here. A CPPM is found in four of the Messapus species described here, as well as M. natalis , but is absent from M. martini and M. meridionalis sp. n., and may be of phylogenetic significance.

Messapus martini possesses feathery setae (FS) on the body and legs ( Figs 11–18 ) typical for Corinnidae . Here we report on the presence of squamate setae with brachia (SSB; sensu Murphy 2007: 30, fig. k; see also Bonaldo 2000: figs 44, 46, 48 and Ramírez 2014: figs 92H, I, 93D, G for possible homologs) for the first time in the genus. These setae cover most of the body and legs in M. tigris sp. n. but are not reported in the other Messapus species treated here. In M. tigris sp. n., SSB are found from the coxae to the proximal region of the tarsal segments ( Figs 23–28 ), with the brachiae of the SSB increasing in length along the length of the tarsi so that the distal setae have a relatively narrow shaft and long brachiae ( Fig. 27 ), similar to the FS typical of other species in the genus, although with a slightly thicker shaft. While the SSB are the dominant setal type, there are also scattered elongate scales with fine longitudinal striae present (e.g. Figs 24, 26 ). The FS of M. meridionalis sp. n. are similar to those of M. martini , but those of the other Messapus species are somewhat intermediate between the extremes presented by M. martini and M. tigris sp. n., and have a thicker shaft and slightly shorter brachia than those seen in M. martini . We consider these to be FS rather than SSB.

The femora, tibiae and metatarsi are usually armed with relatively narrow, elongate spines with fine barbs ( Figs 14–16 , 23, 25 ). Femora, patellae ( Fig. 24 ) and tibiae with dorsal lines of naked rugose cuticle. Patellar indentation narrow, with proximal lyriform organs ( Figs 17, 18 ). Tibiae, metatarsi and tarsi with scattered dorsal trichobothria. Metatarsi with distinct dorsal vibration sense organ at distal end ( Fig. 16 ). Tarsal claws paired, with several small teeth, claw tufts dense ( Figs 19 , 28 ); tarsi with tactile setae, chemosensory setae, trichobothria, a single tarsal slit sensilla and several small pores ( Fig. 27 ); trichobothria with sunken distal plate, tarsal trichobothria with more ridges ( Figs 20 , 29 ) than metatarsal trichobothria ( Fig. 21 ); tarsal organ oval, finely wrinkled, only slightly elevated from surrounding integument, with an oval opening containing nerve endings ( Fig. 22 ); tarsal pores sunken from cuticle, forming near circular pit ( Fig. 30 ); tarsal slit sensillum small, with elevated ridges ( Fig. 31 ).

Figures

FIGURES 3 – 10. Digital microscope photographs of Messapus species, female right chelicerae in posterior view (3) and dorsal habitus (4 – 10): 3, 8 M. tigris sp. n., female; 4 M. megae sp. n., female; 5 Same, male; 6 M. meridionalis sp. n., female; 7 M. seiugatus sp. n., female; 9 M. tropicus sp. n., female; 10 Same, male. Scale bars: 3 = 1 mm, 4 – 10 = 2 mm. Abbreviations: CPPM—cheliceral promarginal pronounced mound; F—fang; P—paturon; PMT—promarginal teeth; RMT—retromarginal teeth.

FIGURES 11 – 22. Scanning electron micrographs of Messapus martini Simon, 1898 subadult female: 11 Eye region, dorsal view; 12 Detail of feathery setae in eye region; 13 Same, anterior dorsal abdomen; 14 – 16 Spines and feathery setae on femur (14), tibia (15) and metatarsus (16) of leg I; 17 Patella I, patellar indentation (PI); 18 Same, detail of lyriform organ at proximal end of PI; 19 Tip of tarsus III; 20 – 21 Trichobothrial bases on tarsus I (20) and metatarsus III (21); 22 Tarsal organ, leg III.

FIGURES 23 – 31. Scanning electron micrographs of Messapus tigris sp. n. female, leg III: 23 Femur, spine, elongate striate scales (ESS) and squamose setae with brachia (SSB); 24 Patella, SSB, ESS and rugose longitudinal dorsal lines (RL); 25 Tibia, spine, SSB and ESS; 26 Metatarsus, SSB and ESS; 27 Distal part of tarsus, indicating trichobothriae (TR), tarsal pores (TP), tarsal slit sensillum (TS), tactile setae (TaS) and chemosensory seta (CS); note the much longer brachia and narrower shafts of the SSB in this part of tarsus; 28 Tarsal claw; 29 Proximal tarsal trichobothrium; 30 Tarsal pore; 31 Tarsal slit sensillum.