Metriocnemus cavipenis Donato, 2023

Donato, Mariano, Zanotto Arpellino, Juan Pablo & Siri, Augusto, 2023, Revision of the species described in Metriocnemus van der Wulp (Diptera: Chironomidae) by Edwards (1931), with the description of two new species, Journal of Natural History (J. Nat. Hist.) 57 (13 - 16), pp. 904-923 : 914-915

Metriocnemus cavipenis Donato sp. nov.

Male imago (n = 1)

Material examined

1 J holotype, ′ Argentina: Rio Negro , Parque Nacional Nahuel Huapi, río Ñirihuau, 41° 17 ʹ 35.1″S, 71°14 ʹ 26.3″W, 1044 m asl ., 15/ 28 .ii .2007, Malaise trap. A . Garré and M . F. Montes de Oca leg. ( MLP)̍.

Total length 2.6 mm. Wing length 2.3 mm. Total length/wing length 1.13. Wing length/ length of profemur 2.31. Colouration uniformly dark brown with legs light brown.

Head. Antennae with 13 flagellomeres, ultimate flagellomere 553. AR 1.32. Temporal setae 40. Clypeus with 16 setae. Tentorium and stipes not measurable. Lengths of palpomeres: 60; 62; rest of palpomeres lost.

Thorax. Antepronotum with 20 lateral setae. Dorsocentrals 52; acrostichals 26; prealars 29; supraalars 2. Scutellum with 34 setae. Preepisternals absent.

Wing ( Figure 1 (b)). VR 1.24. Brachiolum with 9 setae; Sc without setae; R 63; R 1 34; R 4+5 89; RM 2; M 13; M 1+2 52; M 3+4 24; Cu 49; Cu 1 26; Pcu 55; An 40. C extension 160, squama with 18 setae.

Legs. Spur of front tibia 78 long; spurs of middle tibia: 34 and 38; of hind tibia not measurable.Width at apex of front tibia 58; of middle tibia 56; of hind tibia not measurable. Comb not measurable. Tarsomere 1 of middle and hind leg each with 2 pseudospurs; tarsomere 2 of middle leg with 1 pseudospur. Lengths (in μm) and proportions of legs in Table 4 .

Hypopygium ( Figure 2 (c)). Anal point absent. Setae on tergum IX 30, laterosternite IX with 5 setae. Phallapodeme 100 long; transverse sternapodeme 66 long. Virga absent. Penis cavity sclerotised and conspicuous ( Figure 5 ). Gonocoxite 270 long; inferior volsella strongly projecting, ending at 0.82. Gonostylus 122 long; crista dorsalis very low; megaseta 16 long. HR 2.21; HV 2.13.

Etymology

Named after the presence of a sclerotised penis cavity in the hypopygium.

Diagnosis

The presence of the sclerotised penis cavity together with the absence of anal point and virga allows the differentiaton of M. cavipenis from the other species of the genus.

Remarks

The species M. cavipenis was collected in the ecotone between the Subantarctic and Patagonian biogeographic provinces ( Cabrera and Willink 1980). The features of the former province were described above for M. griseovittatus ; the Patagonian province occurs from east of the Southern Andes to the Atlantic coast in Argentina, also extending to Chile in some places. The landscape comprises plateaus, hills and valleys. The climate is dry and cold temperate. Patagonian steppe is the dominant vegetation.

Figures

Figure 1. Metriocnemus wings. (A) M. fasciventris Edwards; (B) M. cavipenis sp. nov.; (C) M. tucumanus sp. nov. Scale bars: 100 µm.

Figure 2. Metriocnemus male genitalia. On the left, dorsal aspect; on the right, hypopygium with anal point and tergite IX removed. (A) M. fasciventris Edwards; (B) M. griseovittatus Edwards; (C) M. cavipenis sp. nov.; (D) M. tucumanus sp. nov. Scale bars: 100 µm.

Figure 5. Metriocnemus cavipenis sp. nov. Detail of the pennis cavity in the hypopygium.