Triogma kuwanai
Creators: name: Imada, Yume
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Cylindrotomidae
Triogma
Triogma kuwanai

description: TRIOGMA KUWANAI (ALEXANDER, 1913)
(FIGS 1A, 2C, 5H, 6G, 17A–F)
Notes: Triogma kuwanai used to be subdivided into two subspecies, T. kuwanai kuwanai (Honshu) and T. kuwanai limbinervis (Shikoku), but T. limbinervis Alexander, 1953 can be treated as a species (Oosterbroek 2020). The accounts below are based on T. kuwanai kuwanai.
Life history: In Japan, adults often fly together with species of L. mikado, L. serraticornis and L. brevipecten at the same locality and about the same period of time (May–June, in Honshu). Larvae are found in moss patches on the forest floor. The cuticular surface is heavily armoured with debris and epibionts, which seems to be related to the cryptic habitat.
Adult behaviour: Three adults were observed on 18 May 2016, Ikawa-touge, Shizuoka, Japan. They occasionally flew over the shaded forest floor when disturbed, but soon returned to the original position. Adult males generally perched on a moss mat, whereas females usually rested hanging on branches or near the damp soil. Eggs were laid on the leaves of the following plant species: Pohlia longicolla (Hedw.) Lindb. (Bryaceae) (four eggs), Mnium heterophyllum (Hook.) Schwaegr. (Mniaceae) (two eggs), Plagiothecium curvifolicum Limpricht (Plagiotheciaceae) (one egg), young shoots of Stellaria media (two eggs) and a sprout of an unidentified species of fern (one egg). Two eggs were laid on the shallow layer of soil. Larvae hatched 10–11 days later from 20 out of 29 eggs. Three larvae perforated and fed on the leaves of M. heterophyllum. All reared larvae died before reaching the second instar.
Egg: Length 1.3 mm (N = 1). Spindle-shaped, circular in cross-section, with a tapered front pole. Pale grey due to exochorionic sculpture, with yellowish tint of egg content (Fig. 2C), yet apparently lighter than L. brevipecten. Chorionic sculpture elongated and narrow, arranged as irregularly jagged, dotted dash lines; reticulated near micropyle.
First-instar larva: Length 2.9 mm (N = 4). Hyaline (Fig. 17D). Dorsal elongated cuticular lobes on thoracic and abdominal segments acutely bent backwards (or occasionally forward).
Final-instar larva: Body with dark brown hue (Fig. 17A). Integument entirely rugulose with velvet-like texture, retaining high opacity in alcohol; dark pigmentation diffused on dorsal side, densest near dorsal lobes, making stripes in parallel with longitudinal body axis; small patch with purple lustre at bases of dorsal lobes (Fig. 17E). Prothorax dorsally with six tubercles along pronotal ridge; one pair of lateral lobes; ventral lobe absent. Meso- and metathorax with two pairs of dorsal lobes, posterior pair bearing two auxiliary outgrowths at the front; two pairs of lateral lobes, anterior pair longer; two pairs of ventral lobes, anterior pair more widely separated from each other than the posterior pair. Dorsal lobes on abdominal segments slender and apices acutely bent backwards (Fig. 6G); four pairs on abdominal segments I–VII, two anterior pairs smallest, and fourth pair longest with three auxiliary outgrowths at front. Lateral lobes relatively long and broad, apices strongly bent backwards. Ventral lobes on abdominal segments relatively long and finger-like (Fig. 17E). Anal segment (Fig. 17C) with one pair of dorsal lobes; dorsomedial lobes absent; two pairs of ventral lobes, anterior pair papilla-like. Spiracular field with hair fringe.
Host-plants: Although larvae are found amid moss tufts of Mniaceae (Bryales), together with Liogma serraticornis, this species probably does not feed on them. One late-instar larva was found feeding on Brachythecium brotheri Paris (Hypnales: Brachytheciaceae). Under rearing conditions, first instar does not survive on the host-plants used for female oviposition (as noted above), including three moss species, Pohlia longicolla (Hedw.) Lindb. (N = 4), Mnium heterophyllum (Hook.) Schwaegr. (Bryales: Mniaceae) (N = 2), Plagiothecium curvifolicum Limpricht (Hypnales: Plagiotheciaceae) (N = 1), although they chew on some leaves of these plants.
description: Published as part of Imada, Yume, 2021, Moss mimesis par excellence: integrating previous and new data on the life history and larval ecomorphology of long-bodied craneflies (Diptera: Cylindrotomidae: Cylindrotominae), pp. 1156-1204 in Zoological Journal of the Linnean Society 193 on pages 1184-1186, DOI: 10.1093/zoolinnean/zlaa177, http://zenodo.org/record/5752755