Axarus cordiformis, Pinho & Dantas & Hamada, 2019

Pinho, Luiz Carlos, Dantas, Galileu P. S. & Hamada, Neusa, 2019, Some notes on taxonomy and distribution of Neotropical Aedokritus Roback and Axarus Roback (Diptera: Chironomidae: Chironominae), Zootaxa 4668 (4), pp. 535-542 : 538-540

Axarus cordiformis sp. n.

( Figure 2 )

Type material. Holotype: male, BRAZIL, Amazonas State , Presidente Figueiredo, Igarapé da Onça, 12.vii.2016, light-trap, GPS Dantas leg. ( INPA).

Etymology. The specific epithet refers to the unique shape of gonostylus, from Latin, meaning heart shaped.

Diagnostic characters. The species can be separated from other Axarus species by the heart shaped gonostylus, almost as wide as long.

Description. Male (n= 1): Total length 7.22 mm. Wing length 3.69 mm. Total length/ wing length 1.96. Wing length/ length of profemur 2.36.

Coloration. Head and legs yellowish. Thorax yellowish with medium brown coloration on lateral vittae, preepisternum, anterior part of scutum and postnotum. Abdomen yellowish with medium brown hypopygium.

Antenna. AR 4.67. Ultimate flagellomere 1.67 mm long.

Head ( Figure 2A ). Temporal setae 20, partly biserial. Clypeus with 20 setae. Tentorium 221 μm long; 98 μm wide. Stipes 196 μm long; 25 μm wide. Palpomere lengths (in μm): 74; 78; 245; 132; 113. Apex of third and fourth palpomeres with 4 apicolateral sensilla each; longest 29 μm long.

Thorax. Antepronotum without setae. Acrostichals 10; dorsocentrals 17; prealars 6. Scutellum with 10 setae.

Wing. VR 1.07. R 2+3 ends about half of the distance between R 1 and R 4+5. Brachiolum with 3 setae; R with 10 setae; R 1 with 2 setae; R 4+5 with 1 apical seta; other veins bare. Squama with 5 setae.

Legs. Scale of foretibia 49 μm long; spurs of midtibia 45 μm and 49 μm long; spurs of hind tibia 39 μm and 45 μm long. Apex of foretibia 167 μm wide; of midtibia 158 μm wide; of hind tibia 187 μm wide. Lengths and propor- tions of legs as in Table 2.

Hypopygium ( Figures 2B, C ). Posterior margin of tergite IX without lateral projections. Anal point 152 μm long; 54 μm wide at its widest point. Transverse sternapodeme 167 μm long. Phallapodeme 304 μm long. Gonocox- ite 515 μm long. Superior volsella tongue-shaped; 127 μm long; 103 μm wide subapically, with long microtrichia projecting mesad and few rather weak setae. Inferior volsella digitiform; 221 μm long; with 36 short and curved setae. Gonostylus heart shaped 196 μm long, 181 μm wide at its widest point. HR 2.63. HV 3.68.

Female, pupa and larva. Unknown.

Distribution. The species is known only from the type locality in Presidente Figueiredo, Amazonas State, Brazil ( Figure 4 ).

Remarks. Besides the shape of gonostylus, A. cordiformis sp. n. shows other remarkable characters such as shortened fourth and fifth palpomeres and unusual leg proportions (LR <1.00 and high values of BV and SV) when compared to others neotropical Axarus (hind leg BV 2.58–3.69 and SV 2.64–3.29, while the new species has BV 5.51 and SV 7.39) due to shorter tarsomeres.

The species somewhat keys to Axarus globosus Donato, Mauad & Andersen in Andersen et al. (2018) by having a large superior volsella but A. cordiformis sp. n. is easily identified by the above mentioned characters.

Figures

FIGURE 2. Axarus cordiformis sp. n., male. A, head, external view left, inner view right, showing tentorium, stipes and cibarial pump. B, hypopygium, dorsal view. C, hypopygium with tergite IX and anal point removed, dorsal view left, ventral view right.

FIGURE 4. Distribution of some Axarus Roback species in South America.