Isotomurus plumosus Bagnall, 1940

Mandal, Pritha, Mandal, Guru Pada, Suman, Kusumendra Kumar, Bhattacharya, Kaushik Kumar & Kumari, Simran, 2024, Taxonomic insight on some newly recorded species of the springtails (Hexapoda: Collembola) from North Eastern and Eastern states of India, Journal of Insect Biodiversity and Systematics 10 (2), pp. 215-229 : 218-219

Isotomurus plumosus Bagnall, 1940 ( Fig. 3)

Material examined. One specimen, India, Arunachal Pradesh, West Kameng district, 2.9 km away from Kunzang choekhor ling Monastery , collected from leaf litter, 27°15'31.1"N, E 92°24'26.5"E, 2340 m a.s.l., 27-III-2023, leg. G. P. Mandal, reg no.- 3426/H14 .

Diagnosis. Adult body length about 1.92 mm. Antennae: head diagonal- 1.24: 1. Ground colour pale yellow, with dorso-median line of dark purple pigmentation; in our specimen, the lateral longitudinal lines are faintly coloured on Abd.I–IV. Lateral black patch prominent on the Abd. VI. Head with median blue patch and basal blue diffused pigment. Antennae become gradually darker to the apex. Legs with differential pigment patches ( Fig. 3A). Antennal segment ratio as I: II: III: IV- 1: 1.7: 1.8: 2.5. A prominent pin chaeta at tip of Ant. IV ( Fig. 3B), Ant. III organ with two curve rods, base of Ant. I with four smooth chaetae. PAO bean shaped, 0.5 times of nearer omma. Lateral process of the labial palp not reaching the base, Md and Mx well developed. Unguis with a lateral and without any internal teeth, Emp. unarmed ( Fig. 3C). VT not clearly visible. Ventral side of manubrium near dens with 3+3 conspicuous spinous chaetae. Dens: mucro ratio- 18.5: 1. Mucro quadridentate with chaetae.

Distribution in India. Arunachal Pradesh (West Kameng)

General distribution. Arctic, Sub-arctic, Europe, West & Central Asia, Mediterranean, North America, and New Zealand ( Bellinger et al., 1996 –2024).

Remarks. This species is quite similar to I. palustris (Muller, 1776) in colour pattern and mucro shape, unlike I. plumosus has a lighter lateral colouration, and a more prominent middle dark blue band and a distinct chaeta present at the base of mucro.