Euanoma starcki Reitter, 1889

Kazantsev, S. V. & Zaitsev, A. A., 2017, Description of larva of Euanoma starcki Reitter, 1889 (Coleoptera: Omalisidae), Caucasian Entomological Bulletin 13 (1), pp. 51-52 : 1-2

Euanoma starcki Reitter, 1889

(Color plates 3, 4; Color plate 5: 9–14)

Euanoma starcki Reitter, 1889: 99 .

Material. 1 specimen, last (?) instar larva, NW Caucasus, Krasnodar Region, Adler district, E slope of Iegosh Mt., upper Byuryuchka River , 800– 900 m, 43°42ʹ00ʺN / 40°00ʹ02ʺE, 29.04.2013, sifting litter and rotten wood from decayed beech stump (K.V. Makarov, A.V. Matalin, A.A. Zaitsev leg.) ( MSGU) ; 2♂, NW Caucasus, Sochi National Park, Chvizhepse valley , 500– 700 m, ca. 43.67°N / 40.06°E, 14.06.2014 (S.V. Kazantsev leg.) ( ICM) .

Description. Last (?) instar larva. Body elongate, almost parallel-sided in thorax and abdominal segments I–V, subcylindric. Upper side brown; sclerites of underside light brown to testaceous; legs yellowish. Body length 8.2 mm (Color plate 3: 1, 2).

Head large, transverse, not retractable into pronotum. Head capsule closed ventrally, gula short; dorsally divided by Y-shaped front sutures into 3 sclerites: triangular anterior plate (with 2 long setae) and a pair of lateral sclerites (each with at least 6 setae dorsally). Dorsal plate with one pair of small stemmata located at lateral edges posteriad of antennae. Tentorium represented by a pair of narrow vertical rods, not attaining to dorsal plate (Color plate 4: 3–8).

Antennae 3-segmented, non-retractable, antennomeres 1–3 elongate, relatively narrow; antennomere 2 ca. 1.5 times longer than antennomere 1, bearing well-developed conical sensorium; antennomere 3 small, tapering; all antennomeres with numerous setae. Mandibles large, separated by less than their width at base, proximally narrowing and bent downwards, minutely serrate at distal half on inner surface, non-setiferous, with both condyles on dorsal plate of cranium and their distal part, together with labrum resting on galea. Labrum elongate, narrow, divided by median groove, with longitudinal rows of setae. Maxillae with prominent stipes; maxillary palps 4-segmented, all palpomeres short, transverse, noticeably diminishing in size distally. Galea elongate, lying between maxillary palps and above labium, bearing one prominent seta and several minute setae in distal part. Labium small, with undivided prementum; labial palps 3-segmented, palpomeres 2–3 transverse, palpomere 3 conical; ligula minute (Color plate 4: 3–8).

All thoracic terga divided by narrow median suture (Color plate 3: 1). Thoracic pleuron consisting of epipleurite and pleurite (both absent on prothorax), and well developed episternum and epimeron. Mesothoracic epipleurite entire, bearing functional trilobe spiracle (Color plate 5: 11, 12). Metathoracic epipleurite entire, spiracle rudimentary. Thoracic sterna consisting of obscure presternites and undivided pro-, meso- and metasternum, each with 2 pairs of setae (Color plate 3: 2).

Legs 5-segmented, coxa elongate, with numerous setae. Trochanter not divided. Tibiotarsus with a pair of short setae (Color plate 3: 2).

Abdominal tergites I–VIII completely divided by dark narrow median line,with numerous long setae (Color plate 3: 1), abdominal tergite IX without median line, conspicuously produced distally into unpaired parallel-sided urogomphus, noticably emarginate at apex; abdominal segment X elongate, tubular, located at ca. 45° to central line, with membranous grooming organ, bearing shorter setae than preceeding sternites on rim of sclerotised proximal part

(Color plate 3: 1; Color plate 5: 9, 10). Epipleurite in abdominal segments I–VIII large, entire. Abdominal spiracle identic to mesothoracic spiracle, present in segments I–VIII,located between tergite and epipleurite. Abdominal segments I–VII with triangular elongate hypopleurite (Color plate 3: 2; Color plate 5: 10, 13, 14). Abdominal sternites I–VIII entire, with numerous setae (Color plate 3: 2); abdominal sternite IX with 1 row of setae, abdominal segment X with 2 rows of shorter setae (Color plate 5: 9, 10).

Diagnosis. The larva of Euanoma starcki is quite similar to the Omalisus fontisbellaquaei Geoffroy, 1785 larva [ Bertkau, 1891; Burakowski, 1988] in the shape and structure of the head, mandibles and antennae, at the same time readily separable by the conspicuous frontal sutures, 3-segmented labial palps and prominent non-paired urogomphus (Color plate 3: 1, 2; Color plate 4: 3–8; Color plate 5: 9–14).

Biology. The unique specimen of the Euanoma starcki larva was collected by sifting rotten wood from a decayed beech stump and litter around, where numerous Trachysphaera sp. (spp.?) millipeds were observed. As Omalisus fontisbellaquaei larvae are known to feed on Glomeris sp. millipeds, inserting their head into the prey and sucking it out [ Burakowski, 1988], it is possible that a similar relationship exists between the Euanoma starcki larvae and Trachysphaera sp. The similarity of their mouth parts also tesify to the plausability of such assumption.