The subclass Acari, comprising ticks and mites, represents one of the largest and most biologically diverse groups within the Arachnida. Among these, eriophyoid mites are a highly specialized group of phytophagous (plant-sucking) pests of global agricultural and ecological concern 1234. These micro-arthropods cause severe mechanical damage to various plant organs and act as vectors for destructive plant viruses transmitted during feeding 567.

To document the diversity of this fauna, field surveys were conducted across two districts of North Bengal, India—namely Malda and Dakshin Dinajpur, situated within the Sub-Himalayan tract—during October and November 2024. Morphological examination of specimens collected from Holarrhena pubescens Wall. ex G.Don (Apocynaceae) revealed a novel species belonging to the genus Diptilomiopus Nalepa, 1916.

Holarrhena pubescens, commonly known as kurchi or kutaj, is a critically important medicinal tree species indigenous to India. This large deciduous tree is widely distributed across riverine beds throughout the Sub-Himalayan tract, spanning from the Indus River to Assam, as well as adjacent Himalayan valleys. The leaves, stem bark, and seeds of H. pubescens are foundational resources in Ayurvedic medicine 8.

Concurrently, numerous phytochemical compounds extracted from this plant have been cataloged by the Ministry of Ayush (https://www.ayush.gov.in). Recent pharmacological evaluations have validated their efficacy, demonstrating analgesic, antibacterial, antidiarrheal, antidiabetic, antioxidant, antiurolithic, and anti-inflammatory properties 9. Furthermore, contemporary neuropharmacological research highlights its neuroprotective, acetylcholinesterase-inhibitory, and anti-amnesic potential 10.

Based on comprehensive morphometric analysis and a thorough differential diagnosis comparing it with previously described congeners, this mite species is determined to be new to science. Consequently, a detailed taxonomic description is provided herein to formally erect the new species within the genus Diptilomiopus, alongside an account of its host plant interactions. The etymology of the specific epithet adheres strictly to the nomenclature rules established by the International Code of Zoological Nomenclature (ICZN)

Taxonomic description of new species: Diptilomiopus subhimalayansis n. sp. on Holarhena pubescence.

Diptilomiopus subhimalayansis n. sp. is formally described and validated as a phytophagous eriophyoid mite inhabiting Holarrhena pubescens. This description addresses the invalid name Diptilomiopus holarhenansis Sarkar, 2011, which was deemed an unavailable nomen nudum under International Code of Zoological Nomenclature (ICZN) standards, as it was only published in an unregistred Ph.D. thesis. This formal validation provides the necessary, legitimate scientific name for the taxon.

Female (n = 46). Body robust, fusiform, 196.9 (196.9–199.7) long, 84.0 (84.0–87.7) wide; reddish in life. Opisthosoma with four longitudinal ridges and three intervening grooves extending along the anterior two-thirds of the body length (Figure 2 A: LM).

Gnathosoma (Figure 2 A). 23.3 (22.4–23.3) long, abruptly deflected downward; dorsal pedipalp genual seta d 3.7 (3.4–3.7) long.

Prodorsal shield (Figure 2 B: AD). 32.6 (32.6–33.6) long, 59.7 (59.7–60.6) wide, with a distinct anterior shield lobe. Shield design with a complete network of cells; median line incomplete; admedian and submedian lines forming complete cells arranged in four distinct strata over an unequal basal line. Anterior stratum with 12 cells, bisected by the median line; second stratum with 3 cells (one central cell and two subequal, larger lateral cells); third stratum with 3 cells of uniform height but unequal width; fourth stratum with 8 cells of unequal height. Within the fourth tier, the two outermost lateral cells extend anteriorly to touch the first tier of cells. Scapular tubercles and scapular setae sc absent.

Leg I (Figure 2 C). 28.0 (28.0–29.8) long from the base of the trochanter; femur 14.9 (14.9–15.8) long, basiventral femoral seta bv absent; genu fused with the femur; tibia 4.6 (4.6–5.6) long, paraxial tibial seta l' absent; tarsus 7.4 (7.4–8.4) long; paraxial fastigial tarsal seta ft' 33.6 (32.6–33.6) long; antaxial fastigial tarsal seta ft" 31.7 (31.7–32.6) long; paraxial unguinal tarsal seta u' 4.6 (4.6–5.6) long; tarsal solenidion ω 5.6 (5.1–5.6) long, curved downward and knobbed at the apex; tarsal empodium em 7.2 (6.9–7.2) long, deeply divided, each branch 6-rayed.

Leg II (Figure 2 D). 26.1 (25.2–26.1) long from the base of the trochanter; femur 12.1 (12.1–13.0) long, basiventral femoral seta bv absent; genu fused with the femur; tibia 5.6 (4.6–5.6) long, paraxial tibial seta l' absent; tarsus 7.4 (7.4–8.4) long; paraxial fastigial tarsal seta ft' 28.0 (27.4–28.0) long; antaxial fastigial tarsal seta ft" absent; paraxial unguinal tarsal seta u' 4.6 (4.6–5.6) long; tarsal solenidion ω 5.6 (5.1–5.6) long, slightly curved; tarsal empodium em 7.4 (7.1–7.4) long, deeply divided, each branch 6-rayed.

Coxal-genital region (Figure 2 F: CG). Coxae I 22.4 (21.4–22.4) long, contiguous along the midline; coxal surface ornamented with wavy lines near the setal bases; coxal tubercles 1b and setae absent. Coxal tubercles 1a with setae present, situated slightly anterior to a transverse line passing through coxal tubercles 2a; seta 1a 28.0 (26.1–28.0) long. Coxae II 14.9 (14.9–15.8) long, ornamented with two curved lines; seta 2a 43.8 (42.8–43.8) long. External genitalia 20.5 (20.5–21.4) long, 27.0 (27.0–28.0) wide; epigynium ornamented with two parallel wavy lines on each lateral half; seta 3a 6.5 (5.9–6.5) long.

Internal genitalia (Figure 2 G). Internal genitalia characterized by a pair of sub-circular spermathecal pouches and a transverse internal apodeme linked to short spermathecal ducts.

Opisthosoma (Figure 2 A: LM). Dorsum with 68 (66–68) smooth annuli; venter with 85 (83–85) microtubercled annuli. Microtubercles sub-circular, positioned along the anterior margins of the ventral annuli; terminal 9 (9–10) ventral annuli bearing fine microstriations. Setae c2 absent. Setae d 10.2 (10.2–11.2) long, located on ventral annulus 36 (36–37); setae e 7.4 (7.4–8.4) long, located on ventral annulus 54 (54–56); setae f 37.3 (37.3–38.2) long, located on ventral annulus 74 (74–76). Setae h1 absent; caudal setae h2 37.3 (37.3–39.2) long.

MALE. Unknown.

Type Locality: India: West Bengal: Malda, English bazar, Latitude: 24°50′40″ N and Longitude: 87°55′50″ E,

Differential diagnosis: Globally, the genus Diptilomiopus Nalepa comprises more than 71 valid species, with 19 species previously recorded from India 12131415. Morphologically, Diptilomiopus subhimalayansis n. sp. belongs to the species group characterized by a distinct cellular network on the prodorsal shield.

The new species can be readily differentiated from D. davisi Keifer, 1969, D. holmesi (Keifer, 1962), and D. jevremovici Keifer, 1960 by the complete absence of scapular tubercles.

Among Indian congeners, Diptilomiopus subhimalayansis n. sp. closely resembles D. ficusis Chakrabarti & Mondal, 1983 in its complex prodorsal shield ornamentation, but it remains distinct from the latter by possessing a 6-rayed tarsal empodium (7-rayed in D. ficusis) and a uniquely distinct epigynium surface ornamentation.

Furthermore, the new species differs from D. trewier Chakrabarti & Mondal, 1983 by the surface textures of both its epigynium and coxae, as well as its 6-rayed tarsal empodium. It can also be easily separated from D. daulatpurensis Sarkar, 2011 by its 6-rayed tarsal empodium

Relation to host: Mites occur as vagrants exclusively on the abaxial (mid-ventral) surfaces of the leaves. Their intensive sap-sucking activity causes prominent leaf rusting and necrotic brown patches (Figure 2 B). Field observations indicated a high localized infestation severity, with symptomatic patches covering a substantial surface area of the foliage. This heavy physical degradation compromises the structural and chemical integrity of the host tissue, thereby rendering the leaves unsuitable for medicinal and phytochemical applications

The present study contributes a novel species of eriophyoid mite to the global documentation of Eriophyoidea diversity, highlighting its significance as an emerging plant pest. Holarrhena pubescens is a critically important medicinal plant indigenous to the sub-Himalayan region of India. The sap-sucking activity of this mite causes severe mechanical and physiological damage to the foliage, which subsequently retards the growth and nutritional uptake of young plants. Consequently, these taxonomic findings provide foundational data that will assist entomologists and plant protection specialists in developing targeted management strategies to safeguard this economically valuable medicinal resource from phytophagous mite infestations