Redescription of the subgenus Rhithrogeniella Ulmer 1939 (Ephemeroptera, Heptageniidae, genus Ecdyonurus) based on reared specimens from India and Thailand

Rhithrogeniella Ulmer 1939 is treated here as a subgenus of the genus Ecdyonurus Eaton 1868 (s. l.). The subgeneric name Rhithrogeniella is a senior synonym of Afghanurus Demoulin 1964 syn. n., Paracinygmula Bajkova 1975 syn. n. and Nixe Flowers 1980 syn. n. Additional description of Ecdyonurus (Rhithrogeniella) ornatus (Ulmer 1939) is given based on imagines and subimagines of both sexes reared from larvae in India and Thailand; lectotype of this species name is designated. Synonymy of E. (Rh.) ornatus and E. (Rh.) tonkinensis Soldán & Braasch 1986 is established (syn. n.). Male and female imagines and subimagines of an unnamed species of Rhithrogeniella are reported from India.

Contribution to the knowledge of the subgenus Tenuibaetis Kang & Yang 1994 (Ephemeroptera, Baetidae, Baetis s. l.)

The taxon Tenuibaetis Kang & Yang (in Kang, Chang & Yang) 1994 is accepted here as a subgenus of the genus Baetis Leach 1815, but not as a genus. In connection with this, new combinations are established: Baetis (Tenuibaetis) parvipterus (Fujitani et al. 2011) comb. n., Baetis (Tenuibaetis) fujitanii (Kaltenbach & Gattolliat 2019) comb. n., Baetis (Tenuibaetis) himani (Kubendran et al. in Kubendran et al. 2022) comb. n., Baetis (Tenuibaetis) kangi (Kubendran et al. in Kubendran et al. 2022) comb. n. and Baetis (Tenuibaetis) panhai (Suttinun et al. 2022) comb. n. Based on reared material, imagines of both sexes and larvae of Baetis (Tenuibaetis) ursinus Kazlauskas 1963, Baetis (Tenuibaetis) hissaricus Novikova 1991, Baetis (Tenuibaetis) frequentus Müller-Liebenau & Hubbard 1985 (= Indobaetis michaelohubbardi Selva-kumar et al. 2012, syn. n.) and B. (T.) fujitanii are redescribed. B. (T.) panhai is redescribed based on subimago reared from larva. Two new species from Southern India, Baetis (Tenuibaetis) kaltenbachi sp. n. and Baetis (Tenuibaetis) bialatus sp. n. are described based on imagines reared from larvae. A new species from Thailand, Baetis (Tenuibaetis) octomaculatus sp. n. is described based on imagines reared from larvae.

Diagnosis, variability, distribution and systematic position of Labiobaetis pulchellus (Müller-Liebenau & Hubbard 1985) (Ephemeroptera, Baetidae, Baetis s. l.)

A new synonymy to Labiobaetis pulchellus (Müller-Liebenau & Hubbard, 1985) (= L. soldani Kubendran et al. 2014, syn. n.) is established based on examination of imagines reared from larvae in India and Sri Lanka. This species belongs to the tricolor group, which comprises Holarctic species L. tricolor (Tshernova, 1928), L. propinquus (Walsh, 1863), L. calcaratus (Keffermüller, 1972), and some Oriental species.

Contribution to the knowledge of Teloganodidae (Ephemeroptera, Ephemerelloidea) of India

Two new species of Dudgeodes Sartori, 2008 and a new species of Teloganodes Eaton, 1882 are described from India; they are Dudgeodesselvakumari Martynov & Palatov, sp. nov. from Himalayan region (Uttarakhand), Dudgeodesmolinerii Sivaruban, Martynov, Srinivasan, Barathy & Isack, sp. nov., and Teloganodesbarathyae Sivaruban, Martynov, Srinivasan & Isack, sp. nov. from the Tamil Nadu part of the Western Ghats. Thus, for now, the Teloganodidae fauna of India includes 11 species. Dudgeodesselvakumari sp. nov. appears to be significantly extend northward the known distribution of Dudgeodes. Partial COI sequences were used as an initial clustering method to show the relationships of D.selvakumari sp. nov. with other sequenced operational taxonomic units (OTU) of the genus.

A new species of Clypeocaenis Soldn 1978 (Ephemeroptera: Caenidae) from Tamil Nadu, India

Clypeocaenis malzacheri sp. nov. is described from the Kottakudi River in southern India, based on larvae and eggs. Clypeocaenis malzacheri sp. nov. appears to be closely related to C. bisetosa Soldn. The new species is distinguished from this species and other congeners based on the structure of the frons; the structure, setation, and maculation of legs; the shape and orientation of the abdominal tergum II projection; and by the shape and denticulation of abdominal sternum IX. Updated couplets for an identification key to Clypeocaenis larvae in the Indomalayan region are provided. The total number of Clypeocaenis species is thereby increased to twelve in the world and seven in India.

A new species of Nigrobaetis Novikova amp; Kluge, 1987 (Ephemeroptera, Baetidae) from Tamil Nadu, India

Nigrobaetis klugei sp. nov. is described based on nymphs from the Sastha falls of Western Ghats, Southern India. The nymph of Nigrobaetis klugei sp. nov. can be distinguished from other Oriental species of Nigrobaetis by the following combination of characters: (i) dorsal surface of the labrum with 1+3 long simple stout setae on the distal half; (ii) paraproct distally not expanded, with a reduced number of spines on distal margin (three large and two small spines); (iii) paraglossae slender, approximately as wide as glossae; (iv) absence of medioproximal spots in the abdominal tergites and (v) long and pointed triangular spines at the distal margin of abdominal tergites.

A new species of Sparsorythus Sroka amp; Sold, 2008 (Ephemeroptera: Tricorythidae) from Tamil Nadu, India

Sparsorythus srokai sp. nov. is described from the Veerapandi River, Theni district, Tamil Nadu, India based on nymphs of both sexes. The nymphs of Sparsorythus srokai sp. nov. can be distinguished by the following combination of characters: i) presence of lateral setae in each segment of caudal filaments, ii) dorsal surface of labrum entirely covered with scattered ribbon-like bristles, iii) posterior margin of mesonotum reaching abdominal segment III in both sexes, and iv) left prostheca with several pointed teeth apically. The new species is compared with other Indian species: S. gracilis Sroka Sold, 2008, S. sivaramakrishnani Sivaruban, Srinivasan, Barathy, Rosi Isack, 2021 and S. nanjangudensis Muthukatturaja Balasubramanian, 2021. The distributional map and key to the genus Sparsorythus in Southern India are also given.

A new species of Dudgeodes Sartori, 2008 (Ephemeroptera: Teloganodidae) from Megamalai hills of southern Western Ghats, India

Dudgeodes sartorii sp. nov. is described based on nymphs from the Megamalai hills of Western Ghats, Southern India. The nymph of Dudgeodes sartorii sp. nov. can be distinguished from other Indian species of Dudgeodes by i) prothorax with two rounded tubercles; (ii) outer margin of mesothorax with simple setae; (iii) distinct maculae in the distal region of femora; (iv) transverse row of setae on fore femora narrower with blunt apex and (v) dark brownish band on the 5th segment of cerci.

A new charismatic Caenis Stephens, 1835 (Ephemeroptera: Caenidae) from Southern India

Caenis americani sp. nov. is described based on larvae and female imagoes from the Mangalamkombu stream of Southern India. Caenis americani is most likely a parthenogenetic species, in the light of the fact that only females have been collected. The larva can be distinguished from other species of Caenis by the i) shape of the sternum IX and its shagreen field, ii) shape and denticulation of hind claws and iii) lateral lobes of mesonotum distinctly bulged. The phylogenetic relationships of the new species remain unknown, as molecular records of Caenis throughout the Oriental region are largely unknown, and the taxonomically important males are absent.

A new species of Sparsorythus Sroka amp; Soldán, 2008 (Ephemeroptera: Tricorythidae) from Eastern Ghats of Southern India

A new mayfly species, Sparsorythus sivaramakrishnani sp. nov. from the stream of Pullian cholai, Thuraiyur, Namakkal district, Tamil Nadu, India is described based on male and female nymphs. Sparsorythus sivaramakrishnani sp. nov. differs from the closely related S. gracilis by the shape of the left prostheca, the number of bristle-like processes at base of left prostheca, the ratio and shape of right prostheca, the ratio of femur length: width, the size of the female nymph, the mesonotum overlapping in fifth abdominal segment of the female, and by the shape of hypopharyngeal lingua.

A new genus and species of Atalophlebiinae (Insecta: Ephemeroptera: Leptophlebiidae) from Palni hills of the southern Western Ghats, India

A new genus and new species of Atalophlebiinae, Klugephlebia kodai Selvakumar, Subramanian & Sivaramakrishnan, are described based on male and female imagos and larvae from Palni hills of the southern Western Ghats of India. The imago of Klugephlebia gen. n. can be differentiated from all other genera of Atalophlebiinae by having the combination of vein MP forked slightly less than half of the distance from base to margin, MP2 attached at base to vein MP1 by a crossvein, a distinctive shape of the hindwing, dissimilar claws on each leg, and distinctive genitalia structures. The larva can be distinguished from other Atalophlebiinae larvae by having the combination of gills present on abdominal segments 1-7, dorsal and ventral portions of lamellae of gills 1 slender and lanceolate with branched tracheae, dorsal and ventral portions of lamellae of gills 2-7 wider & lanceolate and long & suddenly tapering at apex, fore and mid femora with regular rows of long thin setae on outer margins, denticles on claws progressively larger apically, a distinctive labrum, the maxillary palp short with long setae on third segment, and the third segment of the labial palp with distinct setation. The larvae cling to the underside of boulders in the middle of streams where the boulders lie amidst sand and silt. Updated keys to the genera of south Indian Leptophlebiidae are provided.

Influence of certain forces on evolution of synonymous codon usage bias in certain species of three basal orders of aquatic insects

Forces that influence the evolution of synonymous codon usage bias are analyzed in six species of three basal orders of aquatic insects. The rationale behind choosing six species of aquatic insects (three from Ephemeroptera, one from Plecoptera, and two from Odonata) for the present analysis is based on phylogenetic position at the basal clades of the Order Insecta facilitating the understanding of the evolution of codon bias and of factors shaping codon usage patterns in primitive clades of insect lineages and their subtle differences in some of their ecological and environmental requirements in terms of habitat-microhabitat requirements, altitudinal preferences, temperature tolerance ranges, and consequent responses to climate change impacts. The present analysis focuses on open reading frames of the 13 protein-coding genes in the mitochondrial genome of six carefully chosen insect species to get a comprehensive picture of the evolutionary intricacies of codon bias. In all the six species, A and T contents are observed to be significantly higher than G and C, and are used roughly equally. Since transcription hypothesis on codon usage demands A richness and T poorness, it is quite likely that mutation pressure may be the key factor associated with synonymous codon usage (SCU) variations in these species because the mutation hypothesis predicts AT richness and GC poorness in the mitochondrial DNA. Thus, AT-biased mutation pressure seems to be an important factor in framing the SCU variation in all the selected species of aquatic insects, which in turn explains the predominance of A and T ending codons in these species. This study does not find any association between microhabitats and codon usage variations in the mitochondria of selected aquatic insects. However, this study has identified major forces, such as compositional constraints and mutation pressure, which shape patterns of codon usage in mitochondrial genes in the primitive clades of insect lineages.