New records of Hydropsychidae (Trichoptera: Insecta) from India with morphological redescription and preliminary molecular notes on two Macrostemum species

ABSTRACT

We report three new country records of the genera Hydronema Martynov 1914, Hydropsyche Pictet, 1834, and Macrostemum Kolenati, 1859 in India based on newly collected specimens. Hydropsyche diktynna Malicky and Chantaramongkol, 2000 is reported from Badasgam–B, Jammu and Kashmir; Hydronema persica Martynov, 1914 is reported from Leh, Ladakh (new record of the genus for India) and Macrostemum fenestratumAlbarda, 1887, from Andaman and Nicobar Islands, India. Macrostemum floridum Navás, 1929, a species already known in India, is redescribed based on specimens collected from Andaman and Nicobar Islands, significantly extending the known range of the genus. Two species Macrostemum fenestratum and Macrostemum floridum were subjected to morphological examination and DNA barcoding using the mitochondrial COI gene, because the identification of both species is challenging, due to cryptic morphology. This study presents the first preliminary molecular investigation of Hydropsychidae in India. With these additions, the family Hydropsychidae is now represented in India by 246 species and 16 genera.

Keywords:
DNA Barcodes; Hydropsyche; Hydronema; Macrostemum; South Asia

1 Introduction

The insect order Trichoptera, or caddisflies, comprises more than 17,000 described extant species (Morse, 2025). During the last two decades, an increasing number of studies have been conducted, particularly in South Asia on the caddisfly family Hydropsychidae, with systematic (Malicky and Chantaramongkol, 2000; Malicky, 2006, 2007a, 2007b, 2012, 2014; Mey, 1995, 1998, 1999, 2003, 2005; Oláh et al., 2008; Oláh, 2010) and phylogenetic focuses (Geraci et al., 2005, 2010; Schefter, 1996, 2005).

Family Hydropsychidae includes 1982 described species and is the third largest taxon in Trichoptera and the most diverse of the net-spinning Annulipalpia. Curtis (1834) established Hydropsychidae, and as with most of the families described early in the history of the order, its taxonomy has changed substantially over the years, achieving its modern definition with the work of Ulmer (1907). Five subfamilies are currently recognized: Arctopsychinae, Macronematinae, Hydropsychinae, Diplectroninae, and Smicrideinae. In India, this family is represented by 15 genera and 243 species (Parey et al., 2024).

The monotypic genus Hydronema Martynov, 1914 was first described by A.V. Martynov in 1914, based on specimens collected in Persia (modern-day Iran) by the explorer Zarudny (Ivanov, 1991), so the type-species was named Hydronema persica. In Martynov's early classification (Martynov, 1914), Hydronema was considered to be closely related to the Cheumatopsyche processuata-amurensis group but also displayed characteristics that allowed its placement in the subfamily Macronematinae. Key features, such as the short discoidal cell, the absence of hairs on the forewings, and the reduction of palps, were considered indicative of Macronematinae. However, certain traits, like the modified male tarsal claws and relatively short antennae, pointed to affinities with the Hydropsychinae subfamily. This mix of characteristics made the genus a potential evolutionary link between Hydropsychinae and Macronematinae, sparking interest in its unique taxonomic classification (Ivanov, 1991). The genus was recorded in Pakistan (Oláh, 1994) and Tajikistan (Salokannel et al., 2019).

HydropsychePictet, 1834, is the largest genus of the subfamily Hydropsychinae. This genus is represented by approximately 600 species globally, and most of these are confined to the Oriental and Palearctic regions (Morse, 2025). The species-specific variation of structural elements on heads, legs, wings and genitalia among the species has been used for the recent discovery and description of hundreds of new species (Léger et al., 2020; Bednařík and Bocak, 2023).

The subfamily Macronematinae currently includes 22 species from India (Pandher, 2024). The genus MacrostemumKolenati, 1859 is well known for its broad distribution across tropical and subtropical regions worldwide. However, records of Macrostemum species from India remain sparse, limiting the understanding of their diversity and distribution in this region. In the genus Macrostemum, two particular species, Macrostemum floridumNavás, 1929 and Macrostemum fenestratum Albarda, 1887, have been the subject of persistent taxonomic uncertainty due to their striking morphological similarity (Uy et al., 2018). While originally described based on minor differences in genitalia, subsequent taxonomic practice has revealed that these diagnostic characters are variable, leading to documented misidentifications and inconsistent species assignments in regional faunal lists (Padial et al., 2010).

Therefore, molecular tools have become essential in taxonomy, playing a crucial role in clarifying species boundaries, detecting cryptic species, and supporting morphological identifications (Hebert et al., 2003). In caddisfly taxonomy, DNA barcoding, particularly through the mitochondrial cytochrome c oxidase subunit I (COI) gene, has significantly improved the precision of species identification and the reconstruction of phylogenetic relationships (Zhou et al., 2009). Although early taxonomic efforts have led to the description of numerous species, the phylogenetic relationships within the genus Hydropsyche are still poorly understood, emphasizing the importance of molecular methods such as DNA barcoding to clarify species limits and evolutionary linkages (Majeed et al., 2025).

This study revises the taxonomy of four species of family Hydropsychidae in the Indian region, offering updated diagnoses and distribution information. The newly recorded Hydropsyche diktynna, Hydronema persica, and Macrostemum fenestratum, are redescribed here, and Macrostemum floridum has its distribution updated with the latest records from India. Additionally, the phylogenetic analysis of Macrostemum fenestratum and Macrostemum floridum is discussed in detail to improve the understanding of the boundaries between these two morphologically similar species.

While this study provides new distributional records and the first molecular data for selected species of Hydropsychidae from India, it is important to note that our sampling is geographically restricted to Ladakh, Jammu and Kashmir, and the Andaman and Nicobar Islands. Consequently, the results presented here should not be interpreted as representative of the full diversity of Hydropsychidae across the Indian subcontinent.

2 Material and methods

2.1 Field sampling

Light traps with ultraviolet or mercury-vapour bulbs (160W) were used to collect specimens from the Northwest Himalaya (Fig. 1) and from Andaman and Nicobar Islands, India (Fig. 2), between April and October, fromf 2019 to 2023. In cases where electricity was unavailable, we used a 15W ultraviolet fluorescent (BL) tube (Bioquip® Products, Inc. USA), powered by a 12-volt rechargeable battery. For a duration of one to four hours, starting at nightfall, these lights were positioned close to the margin of freshwater streams. In addition to being tagged with relevant details, including the date of collection, location, altitude, and the name or names of the collectors, the specimens were stored in 96% ethyl alcohol with a drop of glycerol.

Figure 1
Collection sites across the Northwest Himalaya

Figure 2
Collection sites of Macrostemum fenestratum, new country record, and Macrostemum floridum from the Andaman and Nicobar Islands, India

Photographs of adult species were taken with a Nikon SMZ 25 stereo-zoom Microscope. To examine genital characteristics, the final abdominal segments of one male specimen of each species were dissected and left in a 10% KOH solution for 6–8 hours. Other specimens were also cleared in lactic acid using the procedure outlined by Blahnik and Holzenthal (2004) and Blahnik et al. (2007). Distilled water was then used to flush the cleaned genitalia. Afterwards, the genitalia were studied in 80% ethyl alcohol with a glycerol drop.

An ocular grid, installed in one eyepiece of an Olympus SZX10 stereo-zoom trinocular microscope, was used to create pencil templates for the illustrations, which were then scanned at 600 dpi in greyscale as TIFF images by using Adobe Illustrator. The specimens are deposited in the Zoology Departmental Museum, Baba Ghulam Shah Badshah University (BGSBU), Rajouri, India.

2.2 DNA extraction and polymerase chain reaction

To support morphological identification and provide molecular evidence for species delimitation, DNA barcoding targeting the mitochondrial COI gene (658-bp fragment) was employed. This genetic marker is widely recognized for its effectiveness in species-level identification across diverse insect groups, including Trichoptera.

We amplified and sequenced the standard 5′ region of the mitochondrial cytochrome c oxidase subunit I (COI) gene, which represents the animal DNA barcode and has been extensively used in Trichoptera for species-level identification and phylogenetic studies (Zhou et al., 2007). We selected a single male from Macrostemum fenestratum and Macrostemum floridum species for DNA barcoding and sequencing. We extracted the DNA from each specimen by removing a single leg and utilizing DNeasy Blood and Tissue Kit (Qiagen). The manufacturer's protocol was adjusted as follows: (1) each leg was immersed in a solution consisting of 20 µl of Proteinase K and 200 µl of ATL buffer; (2) the sample was incubated at 56°C in the Proteinase K solution for 14 hours; and (3) an additional 20 µl of Proteinase K was introduced after 6 hours of incubation. The DNA barcode region of the mitochondrial cytochrome c oxidase subunit I (COI) gene was amplified through polymerase chain reaction (PCR). The PCR reaction mixture comprised 3 µl of DNA template, 1 µl of each oligonucleotide primer, 3 µl dNTPs, 4 µl MgCl2, 5 µl buffer, and 0.4 µl Taq polymerase (QiagenTaq PCR Master Mix). The PCR conditions consisted of an initial denaturation at 94°C for 3 minutes, followed by 35 cycles of denaturation at 94°C for 1 minute, annealing at 45°C for 45 seconds, and extension at 72°C for 1 minute and 30 seconds. A final extension was performed at 72°C for 7 minutes. Two sets of primers were used for amplification: HCO-2198 (5'-TAAACTTCAGGGTGACCAAAAAATCA-3') and LCO-1490 (5'-GGTCAACAAATCAAAAGATATTGG-3') (Folmer et al., 1994), and LepF1 (5'-ATTCAACCAATCATAAAGATATTGG-3') and LepR1 (5'-TAAACTTCTGGATGTCCAAAAAATCA-3') (Hebert et al., 2004).

2.3 DNA sequencing

The purified PCR products were subsequently sequenced using an ABI 3730XL or 3130XL sequencer (Biokart Private Limited, Bangalore, India) with BigDye™ Terminator v3.1 (Applied Biosystems).

2.4 Phylogenetic analysis

For the phylogeny, barcode sequences from the genus Macrostemum were retrieved from the NCBI (Table 1). The DNA sequences obtained in this study were deposited in both the Barcode of Life Data Systems (BOLD) and NCBI GenBank. Syringoseca mimica (KF395660) and Crioa hades (HQ949730) were chosen as outgroup species. Phylogenetic trees were constructed using the Neighbor-Joining (NJ) and Maximum Likelihood (ML) methods in MEGA 7.0 (Kumar et al., 2016). The phylogenetic analysis was carried out following the methods described by (Ćukušić et al., 2017). Both interspecific and intraspecific genetic uncorrected pairwise divergences (p-distances) were computed in MEGA 7.0 (Table 2) (Kumar et al., 2016). The number of hypothetical species within the dataset was estimated by analyzing the barcode gap (the difference between inter- and intraspecific genetic distances) using the Automatic Barcode Gap Discovery (ABGD) method (Puillandre et al., 2012). The mtCOI dataset was inserted into the ABGD online platform with the following the default settings: P (prior intraspecific divergence) ranging from 0.001 (P-min) to 0.08 (P-max), with steps set to 10; X (minimum relative gap width) set to 1; Nb bins (for distance distribution) set to 20; the Kimura (K80) model selected, with TS/TV set to 2.0.

Table 1
List of species used for Maximum Likelihood downloaded from NCBI GenBank.

S. No.	Species	Accession No.	Location
1.	Macrostemum fenestratum	PQ456743	India
2.	Macrostemum fenestratum	PQ560531	India
3.	Macrostemum fenestratum	KX104009	Indonesia
4.	Macrostemum fenestratum	KX103082	Indonesia
5.	Macrostemum fenestratum	KY983380	Vietnam
6.	Macrostemum fenestratum	KX106702	Indonesia
7.	Macrostemum floridum	PP250153	India
8.	Macrostemum midas	KX291674	Thailand
9.	Macrostemum midas	KX107290	Thailand
10.	Macrostemum midas	KY983377	Malaysia
11.	Macrostemum midas	KX105231	Malaysia
12.	Leptonema rafita	GU713332	Costa Rica
13.	Leptonema rafita	GU713394	Costa Rica
14.	Leptonema rafita	GU713344	Costa Rica
15.	Macrostemum fastosum	KX106449	China
16.	Macrostemum radiatum	MN608810	Korea
17.	Macrostemum radiatum	KX105508	USA
18	Macrostemum radiatum	MN608809	Korea Republic
19.	Macrostemum radiatum	KY983378	Japan
20.	Macronema burmeisteri	HQ967730	Ecuador
21.	Leptonema amazonense	GU713379	Venezuela
22.	Leptonema amazonense	GU713378	Venezuela
23.	Leptonema chiapense	HM377465	Mexico
24.	Macrostemum hyalinum	HQ967768	Venezuela
25.	Macronema argentilineatum	HQ967728	Brazil
26.	Macrostemum ulmeri	HQ967529	Peru
27.	Macrostemum ulmeri	HQ967773	Costa Rica
28.	Leptonema ekisi	GU713339	Costa Rica
29.	Leptonema ekisi	KX105054	Costa Rica
30.	Leptonema neadelphus	PV553819	Ecuador
31.	Leptonema intermedium	KX105392	Costa Rica
32.	Leptonema intermedium	GU713421	Costa Rica
33.	Leptonema intermedium	GU713419	Costa Rica
34.	Leptonema intermedium	KX105282	Costa Rica
35.	Leptonema menkei	KX107050	Venezuela
36.	Leptonema sparsum	KX140767	Brazil

Table 2
Uncorrected pairwise divergences (p distances) among mtCOI haplotypes (DNA barcode region) of the analysed Macrostemum species in India.

		1.	2.	3.	4.	5.	6.	7.	8.	9.	10.	11.	12.	13.	14.	15.	16.	17.	18.	19.	20.	21.	22.	23.
1	PQ456743 Macrostemum fenestratum
2	PQ560531 Macrostemum fenestratum	0.000
3	KX104009 Macrostemum fenestratum	0.152	0.000
4	KX10308 Macrostemum fenestratum	0.155	0.158	0.002
5	PP250153 Macrostemum floridum	0.192	0.199	0.183	0.185
6	KX291674 Macrostemum midas	0.155	0.157	0.153	0.155	0.164
7	KX106702 Macrostemum fenestratum	0.157	0.155	0.004	0.005	0.183	0.153
8	KX107290 Macrostemum midas	0.162	0.159	0.155	0.157	0.164	0.005	0.155
9	KY983380 Macrostemum fenestratum	0.167	0.165	0.114	0.116	0.197	0.155	0.114	0.153
10	KY983377 Macrostemum midas	0.166	0.167	0.159	0.157	0.164	0.014	0.160	0.009	0.153
11	KX105231 Macrostemum midas	0.164	0.162	0.157	0.159	0.166	0.007	0.158	0.002	0.155	0.010
12	GU713332 Leptonema rafita	0.176	0.191	0.210	0.213	0.173	0.193	0.218	0.191	0.210	0.198	0.193
13	KX106449 Macrostemum fastosum	0.170	0.174	0.189	0.187	0.197	0.105	0.196	0.099	0.190	0.099	0.101	0.219
14	GU713351 Leptonema woldianum	0.178	0.194	0.208	0.210	0.173	0.193	0.215	0.191	0.210	0.193	0.193	0.003	0.219
15	GU713344 Leptonema rafita	0.179	0.194	0.208	0.211	0.168	0.194	0.216	0.191	0.212	0.194	0.194	0.002	0.219	0.002
16	MN608810 Macrostemum radiatum	0.179	0.176	0.170	0.172	0.209	0.167	0.176	0.165	0.155	0.167	0.167	0.211	0.178	0.211	0.214
17	MN608809 Macrostemum radiatum	0.179	0.176	0.170	0.172	0.209	0.167	0.176	0.165	0.155	0.167	0.167	0.211	0.178	0.211	0.214	0.000
18	HQ967730 Macronema burmeisteri	0.174	0.186	0.179	0.177	0.126	0.174	0.187	0.174	0.194	0.167	0.176	0.191	0.183	0.191	0.187	0.196	0.196
19	GU713394 Leptonema rafita	0.181	0.196	0.213	0.215	0.170	0.198	0.220	0.195	0.212	0.198	0.198	0.003	0.219	0.003	0.002	0.214	0.214	0.191
20	GU713379 Leptonema amazonense	0.166	0.167	0.185	0.187	0.136	0.177	0.186	0.172	0.191	0.174	0.174	0.167	0.198	0.170	0.170	0.199	0.199	0.157	0.172
21	GU713378 Leptonema amazonense	0.166	0.167	0.187	0.189	0.138	0.177	0.189	0.172	0.193	0.174	0.174	0.170	0.200	0.172	0.172	0.202	0.202	0.159	0.174	0.002
22	HM377465 Leptonema chiapense	0.179	0.199	0.216	0.214	0.161	0.219	0.223	0.212	0.234	0.212	0.214	0.114	0.212	0.114	0.112	0.226	0.226	0.196	0.116	0.179	0.181
23	HQ967768 Macrostemum hyalinum	0.179	0.184	0.210	0.212	0.190	0.172	0.217	0.177	0.224	0.181	0.175	0.210	0.189	0.210	0.210	0.214	0.214	0.200	0.212	0.168	0.168	0.226

3 Results and discussion

3.1 Systematics

Hydronema Martynov, 1914 NEW RECORD OF THE GENUS IN INDIA

Hydronema Martynov, 1914: 125. Type species: Hydronema persica

Type Locality. Uzbekistan (Oláh and Johanson, 2008); Pakistan (Oláh, 1994) and Tajikistan (Salokannel et al., 2019)

3.2 Hydronema persica Martynov, 1914, NEW RECORD OF THE SPECIES IN INDIA

(Figs. 3a–f)

Figure 3
Hydronema persica, a–f) male genitalia: a) left, lateral, b) dorsal; c) right inferior appendage, ventral, d) phallus left, lateral, e) phallus, ventral, f) adult habitus of H. persica, left, lateral. (AL = Apicolateral lobe of segment IX; AVSLX = Apicoventral setose lobe of tergum X; BX = Body of tergum X; END = Endothecal processes; IG = Interlobular gap of segment X; INF = Inferior appendage (paired); IX = Segment IX; X = Segment X; MK = Dorsomedian keel of segment IX; PH = Phallotheca; SC = Sclerotization).

Hydronema persica Martynov, 1914, 19: 125, 127-129

Hydronema rudolfi Mey, 1986; Ivanov, 1991: 5

Material examined. India: Ladakh Union Territory of India: Leh, Choglamsar, 34°08'83.3"N 77°60'28.1"E, 2589m, 8-vii-2021; 30♂♂; Majeed, Ali & Hussain (ISRL, BGSBU).

Diagnosis.Hydronema persica shows similarity with Hydropsyche nuristanicaSchmid, 1963. In lateral view, both have the segment X elongated, mesally depressed, and apex curved dorsally. The segment IX is straight in H. persica, in lateral view, while in H. nuristanica it is convex.

In dorsal view, H. persica slightly resembles Hydropsyche bauboMalicky, 2000. Hydronema persica has the apicoventral lobes of segment X (AVSLX) setose, curved apically, with a wide interlobular gap; in H. baubo, AVSLX are round apically, with oval-shaped interlobular gap.

Redescription. Adult male. Overall color in alcohol black, scattered pubescence; first antennal segment dark brown, second segment yellowish-brown; legs yellowish-brown; dorsum of head nearly black; maxillary and labial palps light yellow; wings light brown and opaque. Length from tip of head to apices of folded forewings 9.5–9.9 mm (n=30). Length of forewing 8.25–8.5 mm (n=30); length of hind wing 6.4–7.0 mm (n=30).

Male genitalia (Figs. 3a–e). Segment IX (IX) apically sclerotized; longitudinally short and anterolaterally straight, in lateral view; dorsomedian keel (MK) projecting posterad; posterolateral lobe produced, round and setose, setal fringe continuous with that on posterolateral slope of keel, in dorsal view. Ridge between segment IX and body of tergum X (BX) concave, in lateral view, without depression. Body of tergum X, in lateral view, elongate posteriorly, round apically; apicoventral setose lobes of tergum X (AVSLX) in lateral view long, sinuous, and directed posterad; in dorsal view, tergum X bifid, lobes divergent at mid length, curved mesad, acute apically, with apicodorsal setose lobes (ADSLX) divergent, acute apically; interlobular gap (IG) wide. Inferior appendages (IF) long, basal segment narrow in basal 1/3, wide, twice as thick as base and parallel-sided in apical 2/3, in lateral view; in ventral view, curved mesad, almost straight, broader in apical 1/4. Phallic apparatus straight, broad at base, endotheca (END) long, slender, slightly evaginated near apex, with phallotheca (PH) round, bilobed, apically sclerotized, bipartite, with no spine.

Distribution. Afghanistan, Kazakhstan, Pakistan, Tajikistan, Uzbekistan, and India (Ladakh, India).

3.3 Genus Hydropsyche Pictet, 1834

Type species:Hydropsyche cinerea Pictet, 1834, synonym of Hydropsyche instabilis Curtis, 1834 (designated by Ross, 1944). Synonymy by Geraci et al. (2010).

3.4 Hydropsyche diktynna Malicky and Chantaramongkol, 2000, NEW RECORD OF THE SPECIES IN INDIA

(Figs. 4a–f)

Figure 4
Hydropsyche diktynna, a–f) male genitalia: a) left, lateral, b) dorsal, c) right inferior appendage, ventral, d) phallus, left lateral, e) phallus, ventral, f) adult habitus of Hydropsyche diktynna, right dorsolateral. (D IX X = Depression between segment IX and tergum X).

Hydropsyche diktynna Malicky and Chantaramongkol, 2000, 793, pl. 11

Material examined. Jammu and Kashmir, India: Anantnag, Badasgam; 33°39'1.3"N, 75°14'9.2"E; 09-viii-2022; 3♂♂; Majeed, Hussain, Ali, and Parey (ISRL, BGSBU).

Diagnosis. The male genitalia of Hydropsyche diktynna is similar to that of H. quadrata Li and Dudgeon (1990), in Li et al. (1990) (reported from Hong Kong) and H. askalaphosMalicky and Chantaramongkol (2000) (reported from Thailand). The tergum X, in lateral view, is similar to that of H. quadrata and H. askalaphos (both are quadrate). In dorsal view, the tergum X is more similar to H. askalaphos (in the shape of the median keel, which is produced posterad; apicodorsal setose (ADSLX) lobes are almost similar in shape).. However, in H. askalaphos, each apicolateral lobe (AL) of segment IX is very broad; the depression between segment IX and the body of tergum X is wide, in lateral view; the apicodorsal setose lobe of segment X is round, in dorsal view; conversely, in H. diktynna the apicolateral lobe of segment IX (AL) is narrow; shallow intersegmental depression between segment IX and the body of tergum X, and the apicodorsal setose lobes of segment X are pointed in dorsal view. In H. quadrata, the apicolateral lobe is quadrate; there is a slight depression between segment IX and the body of tergum X; and the apicodorsal setose lobe of segment X is broad in dorsal view. In H. diktynna, the apicolateral lobe of segment IX is triangular, and the apicodorsal setose lobe of tergum X is narrow and pointed, in dorsal view.

Redescription. Adult male. Body color in alcohol brown, with scattered pubescence; antennal segments light brown, dorsum of head brown, maxillary palps brown, labial palps light yellow. Length from tip of head to apices of folded forewings 9.6–10 mm (n=3). Length of forewing 8.9–9.3 mm (n=3). Length of hind wing 6.9–7.3 mm (n=3).

Male genitalia (Figs. 4a–e). Abdominal segment IX longitudinally short; dorsomedian keel directed posterad; anterolateral margin slightly concave subdorsally and posterolaterally angular, with triangular apicolateral lobe. Shallow depression between segment IX and body of tergum X, in lateral view. Body of tergum X quadrate, in lateral and dorsal views; apicoventral setose lobe reduced, directed posterad, in lateral view; apicodorsal lobe triangular, pointed at apices, directed posterad in dorsal view; interlobular gap wide in dorsal view. Inferior appendages long; basal segment 2X as long as apical segment, slightly broader in apical half, in lateral and ventral views; apical segment slightly curved mesad and stout apically, in ventral view. Phallic apparatus with anterior foramen ventrally, anterior part of phallotheca horizontal and broad, narrowing before subapicoventral keel; phallotheca ending distally in circular sclerous endothecal process (END); median rim thickened, incurving, with pair of small irregular phallotremal sclerites located mesally and pre-apically in ventral view.

Distribution. India: (Jammu and Kashmir) and China

3.5 Macrostemum fenestratum Albarda, 1887, NEW RECORD OF THE SPECIES IN INDIA

Macrostemum fenestratum Albarda, 1887: 1877-1879.

(Figs. 5a–e)

Figure 5
Macrostemum fenestratum, a–e) male genitalia: a), left, lateral, b) dorsal, c) phallus left, lateral, d) phallus, ventral, e) Right Wing.

Material examined. India: Andaman and Nicobar Islands, Little Andaman, Krishna nalah, 2.ii.2020, 10°40'6.9" N; 92°32'5.1" E, 28 m, 02-ii-2020, 4♂♂; Dubey, (in Museum, Department of Zoology, BGSB University Rajouri (J&K), India.

Diagnosis. The general shape and structure of the male appendages of this species resemble Macrostemum hestiaMalicky, 1998 (reported from Thailand). In lateral view, both species have the segment IX subrectangular, but they differ in the anterior margin, which is sigmoid in M. fenestratum, whereas in M. hestia it is slightly convex. Further, tergum X is triangular in both species in lateral view, but in M. fenestratum, tergum X is posterolaterally smooth and straight, whereas in M. hestia, tergum X is posterolaterally bulged, with setose lobes in lateral view. In dorsal view, both species have the apical lobe of tergum X well developed and divergent apically. In M. fenestratum, the apical lobes are broad basally and narrow apically. In M. hestia, the apical lobes of tergum X are uniform in width from base to apex, curved mesally outwards, and rounded apically.

Redescription. Adult male. Dorsum of the head dark brown, antenna and maxillary palp pale yellow, adult male brown, in alcohol. Length of maxillary palp 2–2.5 mm (n=4); labial palp 1.5–2 mm (n=4); antenna 22–23.5 mm (n=4); length from tip of head to apices of folded forewings 6–6.8 mm (n=4).

Male genitalia (Figs. 5a–d). Abdominal segment IX convex and broad anterolaterally. In lateral view, setose lobe between segment IX and tergum X present; margin from apical lobe of segment IX to apicoventral lobe of segment IX brown; segment X short, dorsolateral and ventrolateral lobes with stout setae; intersegmental depression flat, with medial setose lobe between segments IX and tergum X; tergum X short, rounded apically. Interlobular gap U-shaped, in dorsal view. Segment X divided mesally, with wide separation and broad apex. Inferior appendage two-segmented, basal segment long, narrow basally, wide sub-apically; apical segment short and robust, rounded apically in lateral view. Phallus with spine-like projection at anterior portion of apex, prominent in dorsal view.

Distribution. Borneo, Cambodia, Java, Laos, Malaysia, Sumatra, Thailand, Vietnam (Uy et al., 2018), India (Andaman and Nicobar) (new record).

3.6 Macrostemum floridum Navás, 1929

Macrostemum floridumNavás, 1929: 777.

(Figs. 6a–e)

Figure 6
Macrostemum floridum, a–e) male genitalia: a) left lateral, b) dorsal, c) phallus, left lateral, d) phallus, ventral, e) Right Wing.

Material examined. India: Andaman and Nicobar Islands, Little Andaman, Krishna Nalah, 2.ii.2020, 10°4'06.9" N; 92°3'2.51" E, 28 m, 02-ii-2020, 5♂♂; Dubey (in Museum, Department of Zoology, BGSB University Rajouri (J and K), India.

Diagnosis. The general shape and structure of male appendages of this species resemble Macrostemum quinquepunctatumBanks, 1920 (reported from the Philippines). Both species have the inferior appendages two-segmented, harpago short and blunt. In lateral view, the phallus has a wide, slightly truncated apex. In ventral view, the phallus has an evident endothecal sclerite. In lateral view, segment X narrows toward the apex, with a setal wart at the tip. In dorsal view, the segment X is divided medially. In Macrostemum floridum, the apicoventral setose lobes of segment X (AVSLX) are divergent, while in M. quinquepunctatum, the AVSLX are produced posterad.

Redescription. Adult male. Dorsum of the head dark brown, antenna and maxillary palp pale yellow, adult male brown, in alcohol. Length of maxillary palp 2.5–3mm (n=5); labial palp 2–2.9 mm (n=5); antennae 24–24.5 mm (n=5); length from tip of head to apices of folded approximately 7–7.4 mm (n=5). Mesoscutum and mesoscutellum lack evident markings.

Male genitalia (Figs. 6a–d). In lateral view, abdominal segment IX convex anteriorly and posteriorly, anteromesal margin smoothly projected anterad; intersegmental depression absent between segments IX and tergum X; segment X short, rounded apically. Interlobular gap V-shaped, in dorsal view. Segment X divided mesally, with wide separation and broad apex. Inferior appendages two-segmented, basal segment short, narrow basally, wide subapically; apical segment long and rounded apically, in lateral view. Phallus with spine-like projections at posterior portion of apex, prominent in dorsal view.

Note. The species was previously reported from only a single specimen collected by Dembicky and Pacholatko in 1997 from Kallar, Kerala, India (Uy et al., 2018).

Distribution. China, Cambodia, Laos, Thailand, Vietnam (Uy et al., 2018), India: (Andaman and Nicobar).

3.7 Distributional comments

This study contributes to the increasing knowledge on the caddisfly fauna of India, particularly within the family Hydropsychidae, which plays a significant role in freshwater ecosystems. The discovery of Hydronema persica, the sole member of its genus previously unknown in India, expands the known range of Hydronema into the Ladakh region of the Indian subcontinent and aligns with its recent report from Kazakhstan (Smirnova et al., 2024). This finding is notable because Hydronema had long been considered confined to Central Asia (Ivanov, 1991; Oláh and Johanson, 2008). Similarly, the first records of Hydropsyche diktynna and Macrostemum fenestratum from Jammu and Kashmir and the Andaman and Nicobar Islands, respectively, further enrich the known diversity of Hydropsyche and Macrostemum, which are broadly distributed across the Palearctic and Oriental regions (Oláh and Johanson, 2008; Oláh, 2010; Malicky, 2012; Morse, 2025). With the addition of these three species, Hydropsychidae is now represented by 246 species across 16 genera in India. These records highlight the importance of systematic surveys in underexplored regions such as Ladakh and the Himalayas, which are likely to harbor additional undiscovered taxa.

3.8 Genetic divergence and DNA barcoding

Analysis of genetic divergences (Table 2) revealed that M. fenestratum exhibited the highest intraspecific divergence (< 16.7%) among its six sequences, while comparatively lower values of intraspecific divergences were recorded in M. midas (< 1.4%), Leptonema rafita (< 3%), and L. amazonense (2%). Macrostemum radiatum showed no intraspecific variation, and in M. floridum, since it was represented by a single sequence, genetic divergences could not be assessed. Interspecific divergences were highest between M. fenestratum and L. chiapense (23.4%), followed by M. floridum and L. chiapense (21.6%). The marked divergence within M. fenestratum suggests potential cryptic diversity, while its strong separation from Leptonema reveals clear taxonomic boundaries.

The observed intraspecific divergence of 16% in M. fenestratum is exceptionally high, compared to values reported for Hydropsychidae in earlier studies (e.g., <5.3% in Geraci et al., 2011; Zhou et al., 2007; Zhou, 2009). Moreover, the minimum interspecific divergence detected here (13.2%) is distinctly higher than thresholds reported for other caddisflies, such as Smicridea (8.05%; Pauls et al., 2010) and Anisogamus (8.2%; Graf et al., 2015). These findings reinforce the utility of COI barcoding for distinguishing Hydropsychidae species in India and highlight the unusual divergence patterns in M. fenestratum.

3.9 Correlation of pairwise distances with the Maximum-Likelihood tree

The ML topology is supported by the pairwise COI distances (Fig. 7). Sequences assigned to the same nominal species generally show much lower pairwise distances and form tight, highly supported clades in the ML tree, whereas inter-generic comparisons show substantially higher divergence. This pattern is consistent with established DNA barcoding principles, where conspecific sequences form tight, well-supported clades, with low pairwise distances (Hebert et al., 2003; Hendrich et al., 2015), while comparisons between genera are characterized by substantially higher sequence divergence (Leray et al., 2013; Hebert et al., 2004). For example, the two newly generated Indian sequences of M. fenestratum (PQ456743, PQ560531) are identical to each other (0.000) and cluster together with full bootstrap support in the tree. By contrast, these two sequences show relatively large distances (≈0.15–0.18) to several previously published M. fenestratum accessions (PQ456743–KX104009 = 0.152; PQ456743–KX10308 = 0.155), suggesting deep intraspecific divergence (or potential misidentification/sequence issues that deserve further verification). Conversely, other conspecific groups show the expected low within-species divergence; M. fenestratum GenBank accessions (KX104009, KX10308, KX106702) differ from one another by only 0.002–0.005 and form a tightly supported subclade (bootstrap 100%). Macrostemum midas accessions (KX291674, KX107290, KX105231, KY983377), likewise, show low pairwise distances (0.002–0.014) and form a strongly supported clade (100% bootstrap). Macrostemum radiatum accessions (MN608810, MN608809) are identical (0.000) and group together with maximum support. Inter-generic distances (e.g., Macrostemum vs Leptonema or Macronema) are of larger magnitude (≈0.17–0.22), consistent with the distinct genus-level clades recovered in the ML analysis.

Figure 7
Maximum likelihood (ML) phylogram based on a 658 bp fragment of the DNA barcode region illustrating the relationships within genus Macrostemum, using Syringoseca mimica and Crioa hades as outgroup. The numbers above the branches indicate bootstrap support (BS)

The maximum likelihood phylogeny recovered a paraphyletic relationship for the genus Macrostemum. Specifically, a clade comprising M. hyalinum and M. ulmeri was placed as sister to a clade containing Leptonema, Macronema and M. floridum, separate from the main cluster of other Macrostemum species. The strong clustering of newly generated Indian sequences, with conspecifics from GenBank, validates their identification and expands the geographic distribution of M. fenestratum into the northwest Himalayas.

3.10 Species delimitation (ABGD analysis)

The ABGD analysis partitioned the COI dataset into distinct groups based on pairwise genetic distances (Fig. 8A). The frequency distribution revealed a pronounced peak at low genetic distances (0.00–0.32), corresponding to intraspecific variation, and a broader distribution (0.13–0.27), representing interspecific divergences. The presence of a distinct barcode gap (~0.03–0.13) without overlap between intra- and interspecific distances allowed delineation of Operational Taxonomic Units (OTUs). These OTUs largely corresponded to morphologically recognized species, further supporting the effectiveness of COI barcoding for species delimitation in Hydropsychidae. ABGD (Fig. 8B) consistently identified 8 initial groups (OTUs) across a wide range of prior intraspecific divergence values (P = 0.0010–0.1000). Recursive partitioning further subdivided these groups into 10–19 clusters, reflecting potential cryptic diversity within certain taxa, particularly Macrostemum fenestratum.

Figure 8
(A–B). Pairwise K2P distances (given in percentage) of 36 aligned sequences: a) the histogram created with the K2P model in the Automatic Barcode Gap Discovery (ABGD) analysis. The horizontal axis shows the pairwise K2P-distance, and the vertical axis shows the number of pairwise sequence comparisons. b) Number of the OTUs by the intraspecific prior divergence.

Most species show expected low within-species COI divergence (< ~1–2% in several GenBank clusters here) and high interspecific/intergeneric divergence (≈17–22%), supporting current morphological species delimitations for the majority of taxa.

4. Conclusion

This study expands the documented diversity of Hydropsychidae in India with new records of Hydronema persica, Hydropsyche diktynna and Macrostemum fenestratum, extending their known distributions into previously unsampled regions of the country. DNA barcoding revealed clear species boundaries, with low intraspecific and high interspecific divergences, consistent with morphological taxonomy, while unusually high divergence within M. fenestratum suggests possible cryptic diversity. The strong congruence between pairwise distances, ML phylogeny, and ABGD partitions reveals the reliability of COI barcoding for species delimitation. It emphasizes the importance of continued molecular surveys in underexplored Indian Himalayan ecosystems. In addition, DNA barcodes for several Hydropsychidae species from India were generated (submitted to GenBank and the BOLD Systems database) for the first time.

Nevertheless, the geographic and taxonomic scope of this study is limited, covering only selected regions and a small subset of species. Broader and more systematic sampling, coupled with multilocus approaches, will be essential for developing a comprehensive understanding of Hydropsychidae diversity, distribution, and evolutionary relationships in India.

Acknowledgements

The authors express their sincere gratitude to the Science and Engineering Research Board (SERB)/ANRF, Government of India, for their financial support of this research under the Core Research Grant (CRG) scheme (Sanction Order No. CRG/2020/001494, dated December 1, 2020). The authors are also grateful to Director, Zoological Survey of India, for providing necessary laboratory facilities. We thank Dr. John C. Morse of Clemson University for his valuable suggestions and Prof. Hans Malicky for providing relevant literature.

Data statement

The entire dataset supporting the results of this study is published in the article itself.

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*

Corresponding author. E-mail:[e-mail] (A. Majeed).

Associate Editor:

Fabio Quinteiro

Conflicts of interest

The authors declare no conflicts of interest.

Publication Dates

• Publication in this collection
  17 Aug 2026
• Date of issue
  2026

History

• Received
  22 Sept 2025
• Accepted
  15 Jan 2026