Contributions to Zoology, 77 (4) - 2008Marco A. Bologna; Andrea Di Giulio: Revision of the genus Trichomeloe Reitter, with the description of new species and fi rst instarlarvae (Coleoptera: Meloidae)
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Bionomics

Before the description of T. ovatus, this genus was considered endemic to the eastern Mediterranean. The main sub-range of the genus includes the southern Anatolia (W to Fethyie, Muğla Province, and to the Greek island of Castelorizon, North to Elazig, and East to the Sanli Urfa Province), Cyprus, the entire Levant, S to the North Negev and E to the northern Iraki Mesopotamia (the new species T. mesopotamicus). A second and isolated sub-range, includes only one locality of the extreme southern Tadjikistan. Specimens of T. sericellus from Crimea and Sicily (see Appendix I) represent very doubtful records or relict populations that were never confirmed.

There is minimal information on habitat and other ecological preferences. Almost all the species are adapted to Turanian steppe or semi-desert habitats, and only T. conicicollis and some Western populations of T. chrysocomus and T. deflexus from the Hatay and Adana provinces (Turkey), are living in Mediterranean habitats, particularly in pastures derived from Pinus halepensis forests or maquis. No information is available on the habitat preference of T. ovatus (see type locality of this species).

Most collection sites are located on plains or in hilly areas, but the altitudinal distribution varies from the sea level to more than 1500 m a.s.l. In particular, T. chrysocomus was collected from about 600 to 1600 m a.s.l. on the Nemrud Dagi (SE Turkey); T. conicicollis from sea level to about 200 m a.s.l.; T. deflexus from -150 m (Dead Sea Valley) to about 1000 m a.s.l.; T. mesopotamicus from about 50 to 300 m a.s.l.; T. ottomanus to at least 1000 m a.s.l.; T. sericellus from about - 50 m (Dead Sea Valley) to about 2000 m a.s.l. on Lebanon Mts; T. syriacus from 400 to about 1100 m a.s.l.

Adults are lucifugous and probably also nocturnal, because they are usually found under stones (see also Bodenheimer, 1934); no information is available on their food preference, but probably adults feed on prostrate Asteraceae or on Poaceae, as the wingless species of the genera Meloe and Berberomeloe. Adult occurrence appears to be primarily restricted to late winter and spring. The following adult occurrence is documented: T. chrysocomus from early March to the first half of May, with few records in January and November; T. conicicollis from the second half of April to the first half of May and one record in September; T. deflexus from January to April, with a few records from October to December; T. mesopotamicus in April and May; T. ottomanus one single record in the late March; T. ovatus two records, respectively in March and April; T. sericellus from January to March, with few records in December and April; T. syriacus from January to March.

Sahlberg (1913) listed one female of T. sericellus digging a oviposition hole in the ground as it is typical of other genera of Lyttini, and more generally in the Meloinae subfamily. This behaviour was personally observed in captivity in both T. chrysocomus and T. syriacus. The first instar larva lasts 9-11 days in T. chrysocomus (about 20, according to Cros, 1934) and 17-18 days in T. syriacus. No information is available on the later larval instars and the development and hosts are unknown. According to its morphology, the triungulin is not phoretic, but probably reaches the nest of a bee species, as in other Lyttini genera.

The first instar larva of Trichomeloe. — Compared to other lyttine larvae, triungulins of the genus Trichomeloe lack distinct autapomorphies, except for the peculiar shape of labial palpomere II (Figs 4e-4f), flattened, asymmetrical and slightly enlarged from base to apex. First instar larvae are recognizable by the following combination of characters: larva slightly flattened, setae everywhere short, head rounded, antennae short with large, bulbous and pointed hyaline vesicle (sensorium), mandibles laterally corrugated with smooth cutting edge, maxillary palpomere III flattened, spoon-like, presence of medial tuft of filiform cuticular structures on epipharynx, long ligular setae, last abdominal sternites completely sclerotized, caudal setae relatively short.

FIG2

Fig. 2. Trichomeloe chrysocomus, first instar larva: a) habitus, dorsal view; b) habitus, left lateral view; c) habitus, ventral view. Scale bar = 500 μm.

Description of first instar larva of Trichomeloe syriacus.— Habitus. Triungulin campodeiform; body elongate, subcylindrical, slightly flattened, subparallel-sided, slightly constricted at metathorax and tapered at abdominal apex (segments VIII and IX).

Colour. Uniform brown due to similar sclerotization of head, tergites, sternites, legs and pleurites; lighter posterior area present on meso and metanotum.

Microsculpture. Cuticle reticulate with irregular poligonal meshes.

Measurements. Body length 1.9 mm (from pygidium to labrum); head length 0.3 mm (from occipital foramen to clypeolabral suture), maximum width 0.4 mm, width at base (occipital foramen) 0.3 mm; basal stem of epicranial suture 0.09 mm; diameter of stemma 0.015 mm; antennal length 0.08 mm; antennal terminal seta length 0.18 mm; sensorium length 0.04 mm, maximum width 0,03 mm; labrum width 0.14 mm; prothorax length 0.25 mm, maximum width 0.46 mm; abdomen length 1,0 mm, maximum width 0.5 mm; abdominal terminal setae length 0.4 mm; diameter of spiracles: mesothoracic 0.034 mm, abdominal I-VIII respectively from 0.03 mm to 0.015 mm.

Head (Figs 3a-3b). Rounded, wider than long (width/length = 1.33), subparallel sided, narrowed towards base; basal elevation absent; anterior margin of head slightly convex. Epicranial suture Y shaped; frontal sutures complete to antennal fossae, widely diverging at base (angle about 90°), then parallel and markedly curved laterally at distal third; basal stem of the epicranial suture very long. One small stemma present on each side of head capsule, dorsally placed, slightly convex, irregularly rounded, about half diameter of mesothoracic spiracle. Frontoclypeal region with a total of 14 setae subequal in length; boundary between clypeus and frons with a transverse row (frontoclypeal row, FCR) of 3 pairs of setae; sensory pit between FCR2 and FCR3 ; 4 pairs of setae posterior to FCR, following a curved line paralleling the arms of the epicranial suture (from posterior to anterior setae 1-4); sensory pits present between setae 1 and 2; each epicranial plate, dorsally on posterior half, with 4 very small setae longitudinally arranged in the middle of the plate, with 1 pit at side; 1 seta and 1 anterior pit close to the base of frontal arms, and 3 setae about at the same level lined laterally; 3 setae at the level of stemma: two medial (the closest to the stemma long being the ocular seta, the other short) and one lateral to the stemma; one short seta anteriorly, just behind antennal fossa; ocular sensory pit distinctly anterior to ocular seta and to stemma. Epicranial plate ventrally with 5 setae (3 lined at the level of hypostomal ridge, 2 anterolateral at margin) and 3 pits (2 at each side of mandibular articulation and 1 medial). Gulamentum weakly sclerotized with 2 short anterior setae. Antennae (Fig. 3c) short, laterally directed; antennomere I short, ring-like with 1 dorsal and 1 dorso-lateral sensory pits; II slightly shorter than I and slightly asymmetric, with 3 elongate (2 dorsolateral and 1 medioventral) and 1 very short seta (dorsally, at the base of sensorium), and 2 dorsal pits; sensorium on segment II ventral, large, bulbous, acute at apex, nearly as long as antennomere III and as wide as antennomere II; antennomere III cylindrical, slightly enlarged toward apex, about as long as antennomere I and II together, with a long apical seta (about 3 times as long as entire antenna); 3 subapical setae, 2 dorsolateral and 1 medioventral; one small seta near the base of apical seta, and 1 small medial pit on outer side of the segment. Labrum transverse, with straight anterior margin and rounded sides, with 9 pairs of setae of different sizes and 2 pits, mostly lined along the anterior margin. Epipharynx with slightly protruding medial tuft of elongate cuticular structures (Fig. 3d), surrounded by about 10 pairs of small sensilla. Mandibles (Fig. 3f) robust, with smooth cutting edge, distinctly excavated ventrally; outer margin of mandible distinctly longitudinally furrowed, with 2 lateral setae and 2 sensory pits dorsally lined with the distal seta. Maxillae (Fig. 3e) with 4 setae on stipes, 2 longer distally, and 2 shorter more basal, and 2 pits, one medial and 1 basal; mala simple, lobiform, protruding, with 8-10 thick, pointed setae; maxillary palpomere I short, ring-like, with 1 very small lateral seta and 1 pit ventrally; palpomere II with 2 setae at the two sides, outer seta reaching half palpomere III; palpomere III subrectangular, asymmetric, flattened (somewhat spoon-like), longer than I and II together, with 1 elongate medial seta basally and 1 apical thin sensorial area widely extending on inner margin, composed by 1 long sensory appendix, inserted in a prominent base, and about 20 shorter papillae; outer margin of palpomere III with 1 slender digitiform sensillum and 1 pit; cardo small, transverse, with 1 very small seta almost on lateral membrane. Labium (Fig. 3b) with mentum bearing 2 basal pairs of small setae and 1 pair of sensory pit basally; prementum with 1 pair of setae medially and 1 pair of small setae basally; dorsal subapical pair of ligular setae (Fig. 3d) elongate, between the insertions of labial palpi; labial palpi with outer margin slightly longer than inner margin; palpomere I short and broad, with ventrolateral small seta, II flattened, about twice longer than I, with an apical sensory complex similar to that of maxillary palpomere III but with sensory appendix shorter and stout; 1 sensory pit lateroventrally (outer side).

FIG2

Fig. 3. Trichomeloe syriacus, first instar larva: a) head, dorsal view; b) head, ventral view; c) left antenna, ventral view; d) labrum, ventral view; e) left maxillary palpomeres; f) left mandible, dorsal view; g) prothoracic claw, anterior view; h) apex of abdomen, ventral view. Scale bars: a = 200 μm; b, h = 100 μm; c, d, f = 50 μm; e = 20 μm.

Thorax. Segments transverse, subrectangular, decreasing in width from prothorax to metathorax, with straight anterior and lateral margins and slightly curved posterior margins. Ecdysial line well marked and complete on pro- and mesonotum and absent on metanotum. Pronotum slightly broader than head, 1.84 times wider than long; 13 setae (12 long and 1 short) and 3 pits present symmetrically at each side of the ecdysial line, approximately disposed in 3 transverse, subparallel rows; anterior row (AR) with 4 setae and 4 pits (1 small anterolateral seta on membrane); medial row (MR) with 3 setae and 1 small anteromedial pit, and posterior row (PR) with 5 setae and 2 pits; prosternum with 3 pairs of medial setae of different length, medial pair shorter and posterior pair longer than anterior pair; 4 pairs of small setae lateral to prosternum (2 pairs lateral at the base of coxa, one anterior and one posterior) and 2 pairs of small setae anteriorly on neck ventral membrane. Mesonotum with AR composed of 5 setae, small compared to those of pronotum and 1 slightly posterior pit; MR with 5 setae (2 near the stigma); PR with 5 short setae and 2 pits; 3 pairs of medial setae on mesosternum increasing in length from anterior to posterior, posterior pair very long. Setae of metathorax similar in number, position and relative dimensions to those of mesothorax.

Legs. Slender; coxa short and subconical, with on anterior side: 3 long setae, transversally lined (gradually decreasing in size from the external to the internal), 2 small setae basal and 1 pit subapical; outer side with 1 extremely small seta; inner side with 1 subapical seta and 1 pit; throcanter with 3 setae and 4 pits; 6 setae and 1 pit on femur, the major ventral femoral seta, much shorter than femur; tibiotarsi and claws increasing in length from fore to hind leg; tibiotarsus with 4 longitudinal rows of 4-7 spiniform setae; claws (Fig. 3g) thin, acute and only slightly curved at apex, with 2 sub-basal setae of different length, slightly displaced at base, the distal longer than the proximal seta and approaching apex; surface of claws longitudinally corrugated.

Spiracles. Rounded, internally papillate and spongy; marginal ring (peritreme) slightly protruding and medially denticulate; mesothoracic spiracle anterolateral, about twice as large as the stemma, suboval; abdominal spiracles dorsolateral, on tergites; abdominal spiracle I larger than others and more displaced dorsally; II-VI subequal in size, VII-VIII smaller.

Abdomen (Fig. 3h). Flattened, subparallel sided with transverse, well sclerotised, rectangular terga; abdominal segments VIII-IX distinctly smaller; tergum completely fused with laterotergites on segments IX, only partially or not fused with laterotergites on segments II-VIII (suture well visible at light microscope). Two long posterior setae on laterotergites. Terga with approximately 3 rows of setae transversely lined at each side of the midline; 2 (one medial and 1 lateral) small setae (4 on tergum I) and 1 pit on AR; 2 short medial setae on MR; 6 short setae and 1 submedial pit on PR. PR of tergum IX with second pair from the midline (caudal setae) elongate, about as long as the last three segments. Sternites (Fig. 3h) gradually enlarging from segment I to VII, covering all sternum on segments VII-IX. Each side of sterna with AR and MR with 1 short seta each, and PR with 4 (3 on sternum I) longer setae (the external pair on lateral membrane on segments I-VI). Segment X membranous, tergum with some very small setae transversally lined, difficult to count at microscope; sternum longitudinally divided in 2 rounded lobs (pygopods, Fig. 3h), moderately produced.

FIG2

Fig. 4. Trichomeloe chrysocomus, first instar larva: a) head, dorsal view; b) head, ventral view; c) head, right lateral view; d) left antenna, ventral view; e) mouthparts, left side, ventral view; f) apical sensorial area on right labial palpomere II; g) right abdominal spiracle I; h) prothoracic claw, dorsal view. Scale bars: a-c = 100 μm; d, h = 20 μm; e = 50 μm; f, g = 10 μm.

Comparison with the triungulin of T. chrysocomus.T. syriacus is very similar to T. chrysocomus (see Cros, 1934; new observation on Wadi Al Hasa specimens, Figs 2a-2c, 4a-4h) for most characters except for the followings: head capsule, thoracic and abdominal segments wider ((i) ratio head capsule width/length: T. syriacus = 1.6; T. chrysocomus = 1.2; (ii) ratio maximal pronotum width/length: T. syriacus = 1.8; T. chrysocomus = 1.6; (iii) ratio maximal width/length of I abdominal segment: T. syriacus = 4.1; T. chrysocomus = 3.5)) with straight and subparallel lateral margins; legs slightly shorter; abdomen distinctly tapered only at the last two segments; frontal sclerite basally narrower (ratio length of sclerite/width of sclerite at basis: T. syriacus = 1.0; T. chrysocomus = 1.8); basal stem of the epicranial suture slightly shorter (ratio frontal sclerite/epicranial suture length: T. syriacus = 1.9; T. chrysocomus = 1.5); stemmata about two times wider; antennomere III slightly shorter (ratio antenna/antennomere III lenght: T. syriacus = 2.0; T. chrysocomus = 2.1); and more clavate at apex; spiracles wider; mesothoracic spiracle more oval; caudal setae slightly longer (ratio caudal seta/body length: T. syriacus = 0.2; T. chrysocomus = 0.1).

Larval features and comparison with other Lyttini genera. — The triungulin of the genus Trichomeloe is a typical non-phoretic larva, very similar to that of other genera of Lyttini. The setae are everywhere short and the chaetotaxy is typical of a lyttine first instar larva, except for a greater length of the ligular setae. The medial tuft of filiform cuticular structures on epipharynx seems to be unique in Lyttini, and convergent to those of several genera of the tribe Meloini. Characteristic of this genus is the presence of flattened, spoon-like maxillary palpomere III, with thin and asymmetrical apical sensorial area, by long, stick-like sensory appendix also present in the genera Lydus, Alosimus, Oenas, Lytta and Teratolytta. Apotypic is the modification of the second labial palpomere, flattened and subrectangular, instead of cylindrical, as in most lyttine genera.

The Trichomeloe triungulin shares with Berberomeloe the following characters: head rounded, distinctly sculptured with irregular polygonal meshes, mandibles longitudinally corrugated on outer side (also in Alosimus and Lydomorphus), abdominal sternites well developed and sclerotized, similar shape and relative size of spiracles (denticulate peritreme and funnel-shaped atrium). Trichomeloe differs from Berberomeloe by the relative length of the antennomeres (Trichomeloe with antennomeres I and II shorter and wider), antennomere II with different sensory appendix (in Trichomeloe larger, more bulbous and more pointed), relative size of setae on antennomere II; shape of fore- and mesofemoral setae, presence of abdominal laterotergites, position of abdominal spiracle I, and tergal sclerotization of abdomen resulting in a different colouration of the body (uniform brown in Trichomeloe and two-coloured, yellow-black, in Berberomeloe).