Pseudosmittia luna, Mukherjee & Som & Hazra, 2022

Mukherjee, Tuhar, Som, Dipak Kumar & Hazra, Niladri, 2022, Two new species of Pseudosmittia Edwards, 1932 from India with a key to Oriental species adult males (Diptera: Chironomidae: Orthocladiinae), Zootaxa 5200 (1), pp. 51-62 : 53-56

Pseudosmittia luna sp. n.

LSIDurn:lsid:zoobank.org:act: B18DA818-F5C5-440E-A3D0-8CAF17DF9548

( Figs. 2A–E )

Etymology. From the Latin word ‘ luna ’ meaning, crescent shape; refers to the crescent shaped virga.

Diagnosis. Pseudosmittia luna sp. n. is recognised by the crescent-shaped virga, AR greater than 1.50, slender gonostylus, and broad-based anal point with 8 setae.

Material examined. Holotype male labelled ‘ Pseudosmittia luna sp. n., India, West Bengal, Purba Bardhaman, Burdwan University Campus (23°15′N, 87°50′E), 28.vii.2019, leg. T. Mukherjee’; paratypes 7 males, data same as holotype.

GenBank Accession no. Metazoan COX1: MW 792413 , OP256569 , OP256570 , OP256571 , OP256572

Description

Male imago (n=8)

Total length 1.15–1.21, 1.18 mm. Wing length 0.61–0.68, 0.64 mm. Total length/wing length 1.77–1.88, 1.84. Wing length/length of profemur 2.3–2.47, 2.41.

Colouration. Thorax with two dark vittae; scutellum dark; abdomen pale, legs dark.

Head. AR 1.56–1.59, 1.57; 13 flagellomeres; ultimate flagellomere 216–225, 223 μm long; head width 282– 291, 286 μm; temporal setae absent; clypeus with 4 setae; palpomere lengths (I–V) (μm): 15–19, 18; 15; 29–31, 30; 48–52, 50; 78–81, 80; CA 0.59–0.63, 0.61; CP 1.469–1.574, 1.481.

Thorax ( Figure 2A–B ). Dorsocentrals 8–9, 9; acrostichals 2; scutellars 5–6, 5; prealars 2–3, 3.

Wing ( Figure 2C ). VR 1.3–1.8, 1.6; VR 2 1.52–1.57, 1.55; anal lobe weak; costal extension 5–12, 11 μm; FCu slightly bent; brachiolar 1; wing veins C, Sc, R 1, R 2+3, R 4+5, M, Cu bare; squama bare.

Leg. Spurs on fore, mid, and hind tibia 21–24, 23 μm; 17–18, 18 μm; 28–31, 30 μm long, respectively. Width at apex of fore, mid, and hind tibia 19–21, 20 μm; 18 μm; 21–23, 22 μm respectively. Length and proportions of leg segments in μm given in Table 1 .

Hypopygium ( Figure 2D–E ). Anal point 6–9, 8 μm long; phallapodeme 39–45, 42 μm long; transverse sternapodeme 28–37, 32 μm long; virga ( Figure 2E ) crescent shaped, 26–28, 27 μm long; inferior volsella triangular with no accessory lobes, 51–54, 52 μm long, reaching 0.77–0.78, 0.78 of gonocoxite; gonocoxite 66–69, 68 μm long; gonostylus 38–42, 41 μm long, slender; crista well developed, megaseta 6 μm long. HR 1.78–1.84, 1.81; HV 1.69–2.88, 2.28.

Remarks. Pseudosmittia luna sp.n. belongs to brachydicrana group based on a weak but not reduced anal lobe, a short costal extension, a postcubital fork in wing, reduced or lack of superior volsella, inferior volsella placed posterior on the gonocoxite, and inconspicuous crista dorsalis.

The species is similar to P. christmasensis Ferrington and Saether, 2011 in the shape of inferior volsella. However, anal point of the new species is much smaller than P. christmasensis (20 μm) along with smaller HR (2.02), longer virga (20 μm) and higher AR (0.89). A comparison of some morphological characteristics of adult males among the proposed new species with other species in the genus is provided in table 2.

The K2P distances between the five sequences varied from 0 to 0.01. The average interspecific K2P distances reported from NCBI and BOLD for the genus Pseudosmittia were 0.09 ( Figure 3A ). The average interspecific K2P distance between the genera of the subfamily Orthocladiinae is 0.189 ( Mohammadi et al. 2021). These K2P values were utilised for discrimination and delimitation of the species ( Ekrem et al. 2010). The COX1 sequences of P. luna sp. n. can be differentiated from other sequenced species by more than 10% divergence which is more than the interspecific divergence obtained by ABGD analysis (9.6%). Among all the sequences available at NCBI GenBank, the barcode sequence of the proposed new species showed least divergence with an unknown species with accession number MG301870 . The results are represented in the form of a dendrogram ( Figure 3B ) using K2P and uniform distribution. The distance among the sequences is shown in the form of a matrix (S1)).

Ecology. The species is strictly diurnal. Individuals belonging to the species were never found in light trap collections. Large swarms occur over a marker at a height of about 160 cm. The midges used any object as marker like vehicles, dried leaves, and inflorescence. Swarms were observed to disperse once the markers were moved. Swarming took place under bright sunlight in hot and humid conditions of 86 to 90% and temperatures 35 to 40°C. Multiple swarms in a small area were a common occurrence. Swarming was observed between mid-morning and mid-evening.

Figures

FIGURE 2. Pseudosmittia luna sp. n. male (A–D). A, B.Thorax; C. Wing, scale: 50 µm; D. Hypopygium, scale: 50 µm; E. Virga.

FIGURE 3. A. Histogram of pairwise K2P distances of 23 aligned sequences using ABGD. The x-axis shows the pairwise K2P-distance, and the y-axis shows the number of pairwise sequence comparisons; B. Neighbour-Joining tree based on the COX1 gene sequences of Pseudosmittia luna sp. n. and twenty-eight most similar sequences from NCBI GenBank, Allocladius Kieffer and Hydrosmittia Ferrington & Saether as outgroup. Bootstrap value indicated above the nodes Scale: 0.02 substitutions per nucleotide position.