Microptila orienthula Kjaerandsen & Ito 2009

Ito, Tomiko, 2023, The larva of Microptila orienthula Kjaerandsen & Ito (Trichoptera, Hydroptilidae), with a description of its microhabitat in Japan, Zootaxa 5357 (3), pp. 445-450 : 445-449

publication ID	https://doi.org/ 10.11646/zootaxa.5357.3.7
publication LSID	lsid:zoobank.org:pub:745CDC47-BE00-4292-892A-0A0411BF62BC
DOI	https://doi.org/10.5281/zenodo.10067073
persistent identifier	https://treatment.plazi.org/id/0399F63C-CF09-D477-5D92-F9E3FD21C7AD
treatment provided by	Plazi
scientific name	Microptila orienthula Kjaerandsen & Ito 2009
status

Treatment

( Figs 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Microptila orienthula Kjaerandsen & Ito 2009 , 177–180, male, female, Japan (Hokkaido, Honshu); Ito 2017a, 105–107, male, female, Japan (Hokkaido, Honshu, Shikoku, Kyushu, Yakushima); Ito in press, adult flight period, Japan (Honshu).

Final instar larva ( Figs 1 View FIGURE 1 , 2 View FIGURE 2 , 3D, 3E View FIGURE 3 ).

Body length up to about 2.2 mm in alcohol.

Head ( Figs 1A–1G View FIGURE 1 ). Elongate, sides subparallel, ecdysial sutures indistinct.Width about 0.22 mm; width: length: depth about 1.0: 1.25: 0.85; uniformly brown; longest seta (seta 9 of Wiggins 1996) situated mesal side of eye spot, about 1.5 times head width. Labrum symmetrical with four pairs of setae at anterior half and numerous fine setae on anterior margin. Mandibles robust, asymmetrical, left one with acute apex and long mesal blade distinguished by basal notch, right one with blunt apex and sinuous mesal blade lacking distinguishing notch. Antennae situated mid-way between eye spots and anterolateral corners, each with seta at mid-length and sensillum apically. Dorsal surface densely covered with short hair-like spines (sensu Graf et al. 2004; “minute spinules” of Wells 1985).

Thoracic segments ( Figs 2A–2F View FIGURE 2 ). Pronotum completely covered with pair of brown plates, round at anterolateral corners, concave at posterolateral corners. Each of meso- and metanota covered with a pair of rectangular brown plates. Dorsal surfaces of plates covered with short hair-like spines. Number of setae about 30 on each plate of pronotum, about 20 on each plate of meso- and metanota. Sternites absent.

Foretrochantins and pleura of meso- and metathoraces subquadrate. Thoracic legs similar in structure except foretibiae each with apicoventral lobe with subapicolateral seta, subapicodistal plate with brush of fine hairs, and stout apical spur; femora successively longer from foreleg to hind leg.

Abdomen ( Figs 1A View FIGURE 1 , 2A, 2G, 2H View FIGURE 2 , 3D, 3E View FIGURE 3 ). Slightly compressed laterally, distended, segments gradually enlarging from I to IV (or V) then decreasing, curvature of abdomen slight. Segment I with ellipsoidal tergite, very weakly sclerotized especially at middle, with three pairs of setae on tergite and about 5–6 pairs of setae around tergite; dorsal chloride epithelia on terga II–VIII; large dorsal ellipsoidal sclerite on segment IX; two roundish sclerites on segment X dorsolaterally; anal claws each with two accessary hooks.

Case ( Figs 1I, 1J View FIGURE 1 , 3D View FIGURE 3 ). Compressed laterally, composed of two ellipsoidal valves, with slit openings at anterior and posterior edges, made of silk together with few slender plant pieces. Length up to 3.0 mm.

Diagnosis from other congeneric species. The larva of M. orienthula is very similar to that of a West Palearctic species, M. minutissima Ris , but can be discriminated from the latter by hair-like spines of thoracic dorsal plates; the hair-like spines are present on each of pro-, meso- and metanota in M. orienthula ( Fig. 2B View FIGURE 2 ), but on pronotum and anterior half of mesonotum in M. minutissima ( Graf et al. 2004) .

Microhabitat ( Figs 3A–3C View FIGURE 3 ). The M. orienthula larvae were studied in a hygropetric habitat,Akazawa, Shizuoka, Honshu, Japan (35.0386˚N, 138.2594˚E, 140 m a.s.l.) on 14 April 2023. At this site, 85 males and 25 females of M. orienthula , 985 males of Stactobia japonica Iwata 1930 , 246 males of S. distinguenda Botosaneanu & Nozaki 1996 and many unidentified females of Stactobia were collected with net sweeping efforts during 44 visits by Mr. Toshio Hattori during 2009–2013 (Ito in press).

Microptila larvae were not found on bare, uncovered rock surfaces (where Stactobia pupae and larvae were abundant; Ito in press, figs 1D, 1E) but rather in plant clusters composed of mosses and liverworts, sometimes accompanied by short grasses ( Figs 3B, 3C View FIGURE 3 , indicated by circles). Larvae of many caddisfly taxa, such as Rhyacophila sp. (Rhyacophilidae) , Dolophilodes sp. (Philopotamidae) , Homoplectra sp. (Hydropsychidae) , Micrasema sp. (Brachycentridae) , Helicophyche sp. ( Helicopsychidae ), were also found in the plant clusters. Moreover, water mites, freshwater worms, freshwater crabs, and larvae of various stoneflies and midges were found among these plants.

Four hydroptilid genera, Plethus Hagen 1887 , Pseudoxyethira Schmid 1958 , Stactobia McLachlan 1880 , and Microptila , are found in waterfalls and hygropetric habitats in Japan ( Ito 2017a, 2017b, 2017c; Ito & Saito 2016). Among them, the larvae and cases of Plethus and Stactobia are depressed dorsoventrally and larvae live on bare rock surfaces ( Ito 2017c; Ito & Saito 2016). Their flattened shapes are adapted for life on top of flattened hard substrates in running waters ( Huryn et al. 2008; table 9. A). On the other hand, the larva and case of Pseudoxyethira is compressed laterally and larvae live among mosses in hygropetric habitats and waterfalls ( Cairns & Wells 2008; Ito 2017a). Microptila is the second genus known to inhabit plant clusters of hygropetric habitats and are similar to Pseudoxyethira in their laterally compressed larvae and cases.

Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu, Yakushima).

Specimens examined. Japan, Honshu: 11 larvae, hygropetric habitat, Akazawa , Shizuoka, 14.iv.2023, T. Ito .

Japanese name. Mikuro-hime-tobikera.