Rhathymus atitlanicus, Ayala & Hinojosa-Díaz & Armas-Quiñonez, 2019

Ayala, Ricardo, Hinojosa-Díaz, Ismael A. & Armas-Quiñonez, Ana Gabriela, 2019, A new species of Rhathymus Lepeletier & Serville, 1828 (Hymenoptera: Apidae Rhathymini) from Guatemala, Zootaxa 4700 (1), pp. 132-138 : 135-137

Rhathymus atitlanicus , new species

Figs. 1‒ 6

Diagnosis: Integument and overall pubescence dark brown to black, with small tufts of whitish hairs on upper sides of superior margin of pronotum, posterior trochanter, metanotum and upper part of propodeum. Wings translucent amber with lighter distal ends, contrasting with black color of the body; veins reddish brown, but costal vein, prestigma, stigma and part of marginal vein almost black. Legs with black integument; medial tibia with an elongated tuft well-defined, with dense light brown hairs, on the outside surface, towards the anterior margin, not reaching lateral ends; mid tibia with a spine-shaped projection at posterior distal angle. Integument of mesosoma and metasoma black. Terga entirely black ( Figs. 1–5 ), unlike R. quadriplagiatus (Smith 1860) , where T1 and T2 present each, two very noticeable white setose sublateral spots ( Fig. 7 ).

Description: Holotype female (RA 1017). Body length 20.30 mm; forewing length 14.50 mm; compound eye length 3.20 mm, maximum width 1.90 mm. Overall integument and pubescence dark brown to black. Head: width 5.00 mm, length 3.70 mm. Mandible brown on basal half, black on apex, lower margin with brown hairs; galea long, reaching anterior third of ventral surface of mesepisternum. Labrum wider than long (1.38 mm wide, 1.04 mm long); basal half light brown, lateral bullae translucent, scarcely punctate, apex black with a raised submarginal rim, preceded by an area with more abundant punctures; inferior margin with a row of reddish orange hairs; lateral areas with darker, longer, erect hairs. Malar area very short, 0.13 mm, black except anterior fourth light brown. Clypeus, maximum width 2.40 mm, mid length 0.97 mm; strongly projected respect to eye margin (0.78 mm) (following Brooks [1983]); lower margin slightly concave; integument punctures, elongate, well-marked; integument on lower submargin brighter; lateral areas with noticeable appressed setae; genal area narrow, 0.89 mm in lateral view; upper interocular space 2.31 mm, inferior interocular space 2.72 mm; clypeocular distance 0.26 mm, slightly less than the minimum width of scape; ocellocular distance 0.71 mm; interocellar distance very short; supraclypeal area project- ed, with a sharp cusp between toruli, frontal line reaching the cusp, setae denser and smaller than on clypeus; torulus, width 0.45 mm, length 0.52 mm, intertorular distance 0.70 mm, antennocular distance 0.50 mm; paraocular area with shallow punctures, bright integument and scattered, long, appressed setae; frontal area with punctures larger than on clypeus; anterior ocellus width 0.35 mm, slightly wider than lateral (0.29 mm); ocellocular area, slightly depressed below level of upper margin of compound eye, with smaller punctures than on frontal area, without setae; postero-lateral area of lateral ocelli depressed; vertex slightly above upper margin of compound eye; genal area integument dark brown, setae moderately dense, longer towards lower area, preoccipital ridge faint, looking rounded; hypostomal carina very strong, lamellar. Antenna: Radicle with light brown integument; length of scape 1.16 mm, basal width 0.34 mm, distal 0.67 mm, with a sub-conic prominence on anterior distal end; pedicel short, with black integument and very short black setae. F1 slightly wider than long (0.45 mm; 0.30 mm) shorter than F2 (0.54 mm); remaining flagellomeres similar to F1 except F10 longer (0.78 mm). F1 integument, black on basal third, brown distally, F2 to F10 integument brown (with some dark areas), with whitish micro-setae coming off very small, opaque, alveoles. Mesosoma: Pronotum, integument black, light brown on pronotal lobe, where integument is noticeably polished with scattered punctures; dorsolateral angle and upper margin with long black setae in the middle and whitish on the sides; anterior groove to pronotal lobe well marked. Scutum: mid length 3.60 mm, width (intertegular distance) 3.20 mm, integument, smooth, glossy black, punctuation moderately dense, distance between punctures about one puncture diameter, moderately dense, dark, branched setae coming off the punctures; median mesoscutal line running as a noticeable keel on anterior two thirds of scutum; parapsidal line on mid-posterior area of scutum; lateral margin of scutum with a well-defined carina, posterolateral corner next to axilla noticeably sunken. Tegula more rounded in the anterior part and narrowly toward the posterior; integument hyaline brown, lighter on anterolateral margin, shiny, polished with moderately dense (interpuncture space about two puncture diameters) small, uniform, punctures. Scutellum: Strongly bigibbose, with two prominent cusps, integument smooth glossy, anterior surface moderately punctate (interpuncture space two to three puncture diameters), punctures small (about one third the size of those on scutum). Metanotum: integument and punctation as on scutellum, with white pubescence (black in paratype) and some black setae towards the middle part. Mesepisternum with a midanterior knob-like projection; integument smooth, glossy black, punctuation and pubescence similar to that on scutum, slightly denser; area edging the pronotal lobe, with some lighter, noticeably branched setae. Episternal groove complete. Hypoepimeral area elevated respect to the remainder of mesepisternum, with few punctures towards the anterior end and with shiny integument. Metepisternum with granulate integument in the inferior third, similar to that on lateral areas of propodeum, remaining area with puncture size and distribution similar to that on mesepisternum, but punctures shallower, becoming denser posteriorly. Propodeum: dull respect to scutellum, strongly granulate, especially on the sides, punctation equivalent to that on posterior areas of metepisternum, pubescence slightly less dense than on mesepisternum, setae noticeably branched middle posterior area with longer setae. Spiracle of propodeum slightly curved, length 0.63 mm, width 0.15 mm. Legs: integument dark brown to glossy black, pubescence dark brown to mainly black; tarsi beyond basitarsi with light brown setae, reddish on forelegs; mesotibia with posterior marginal setae longer than those on posterior margin of metatibia; mesotibia with a long tuft of light brown dense setae well defined, on anterolateral margin, not reaching the lateral margins; mesotibial length, 3.06 mm, mesobasitarsus length, 3.10 mm, mesotibia with a sharp spine-shaped projection on posterodistal angle; length of movable spur of mesotibia, 1.60 mm; metatibial length 4.40 mm, metafemur length, 4.37 mm, metabasitarsus length, 3.10 mm; movable outer spur of metatibia shorter than inner one (outer 1.38 mm, internal 1.86 mm). Wings: Length of fore wing 14.5 mm, maximum width 5 mm; membrane color amber hyaline (appearing orange), sharply contrasting with black color of body; costal vein, prestigma, stigma and basal third of Rs vein, almost black, rest of veins reddish-brown, darker towards base of wing; length of marginal cell 3.70 mm, width 0.14 mm; most of the wing covered by dense micro setae, denser towards costal margin, less dense on central area of 2nd cubital cell, and almost absent on vannal lobe; submarginal cells width along submarginal cell, similarly sized (0.75, 0.80 and 0.78 mm); length of Rs-M vein and M on second and third submarginal cells, 1.50, 1.23 and 0.92 mm respectively. Metasoma: Integument in general black; T1 with integument smoother and shinier than following terga; all terga with dark brown to black, short, simple setae; on anterior facing section of T1, with longer, scattered setae; posterior margin of all terga smooth and bare, wider towards middle section; pygidial plate integument very finely reticulate, length 1.57 mm, width 0.75 mm; sterna with integument similar to that of terga, but with pubescence not as dense; S6 projected posteriorly as usual for the tribe, beyond posterior margin of the pygidial tergum.

Male: Unknown.

Type material: Holotype female ( RA 1017 ): Guatemala, Sololá, SLT, Nva Providencia, G 1, 9: 50, 21.vii. 2013, 14.56043, -91.1293, 1030 m, G. Armas P1.45, 17950 . Paratype female ( RA 1018 ) Guatemala, Sololá, SLT, Patzibir, G 2. 10: 20, 20.ix. 2013. 14.61084, -91.1418, 1530 m G. Armas. PL .29, 1070, 18128. Holotype and paratype are deposited in the Colección Nacional de Insectos, Instituto de Biología, Universidad Nacional Autónoma de México, Ciudad de México, México ( CNIN) .

Etymology: The specific epithet refers to Lake Atitlán, in Guatemala, since the known specimens of this species were collected in the mountains around the lake.

Distribution: Although this species is known only from the Sololá region, in San Lucas Tolimán, on the southern shore of “Lago de Atitlán” Guatemala ( Fig 6 ), it is very possible that its distribution is associated with that of the cloud forests and broadleaf forests of the mountain chains between Chiapas, Guatemala possibly even reaching Costa Rica.

Comments: Collecting experience of the first two authors attests for the rarity of the species of Rhathymus in the region, which, like other species of the genus, may be cleptoparasitic of species of the genus Epicharis in the cloud forest of Central America. This species with a very dark integument and amber wings seems to be part of a mimetic complex with other bees such as Odyneropsis apicalis Ducke, 1909 or several wasps, like those of the genus Polistes apicalis Saussure, 1858 or Parachartergus apicalis (Fabricius, 1804) . Only another species of Rhathymus is known for Mexico and Central America, plus a species of Nanorhathymus , the other Rhathymini genus. The new species here described is easily distinguished from R. quadriplagiatus , the other Rhathymus species known for the region, on the basis of patterns of setae coloration on metasomal terga, while Nanorhathymus acutiventris (Friese, 1906) , the other Rhathymini species in the region, is largely yellowish ( Figs. 7–8 ). The low number of know species for the tribe in the region is consistent with the known diversity for Epicharis , taking into account that the species of this genus are parasitized by Rhathymus , however, we believe that in Central America, especially in Costa Rica and Panama, more Rhathymus species can be expected, including some of those already known for South America.

Figures

FIGS. 1–5. Rhathymus atitlanicus new species. 1. Lateral habitus, 2. Dorsal habitus, 3. Head, 4. Scutum and scutellum, 5. Mesotibia. Only female specimens are known.

FIG. 6. Rhathymus atitlanicus new species. Locality records (black dots).

FIGS. 7–8. 7. Rhathymus quadriplagiatus (Smith, 1860), female from Ayutla, Izucar de Matamoros, Puebla, Mexico. 8. Nanorhathymus acutiventris (Friese, 1906), female from Estación de Biología Tropical Los Tuxtlas, Veracruz, Mexico.