Distoleon tetragrammicus (Fabricius, 1798)

Badano, Davide & Pantaleoni, Roberto Antonio, 2014, The larvae of European Myrmeleontidae (Neuroptera), Zootaxa 3762 (1), pp. 1-71 : 24-26

Distoleon tetragrammicus (Fabricius, 1798)

( Fig. 3C , 4C , 12 )

The first report about a not pit-building antlion larva regards almost surely this species ( Réaumur 1742; Bonnet 1780) but the first accurate scientific description was realized much later by Brauer (1854), subsequently it was redescribed many times ( Hagen 1873; Redtenbacher 1884; Steffan 1975; Satar et al. 2006, Krivokhatsky 2011).

Examined specimens. France. Gard, Générac , arenaceous escarpment, VIII.2011 (D. Badano), 15 L1: 10 laboratory-reared to L3, 5 laboratory-reared to adults . Italy. Val d’Aosta, Aymavilles (Aosta), Pont d’Ael , rock overhang in arid meadow, VIII.2011 (D. Badano), 1 L3. Veneto, Bovolone (Verona), V.2010 (F. Sanna), 1 L3. Liguria, Perinaldo (Imperia), stone wall, VII.2011 (D. Badano), 3 L3 and 1 L3 laboratory-reared to adult. Liguria, Pompeiana (Imperia), rock escarpment, VII.2010 (D. Badano), 1 L3. Liguria, Cipressa (Imperia), Mediterranean scrubland, under pine trees, I.2012 (D. Badano), 4 L3. Tuscany, Elba, Portoferraio (Livorno), IX.2010 (L. Forbicioni), 1 L3. Lazio, Rocca Priora (Roma), X.2011 (M. Gigli), 1 L3. Sardinia, Berchidda (Sassari), cork oak wood, pitfall trap, VII.2010, (M. Verdinelli & S. Cossu), 1 L3 . Greece. Corfu, Kato Pauliana , rock overhang, V.2012 (D. Badano), 1 L3 .

Description of 3 rd instar larva. Size (based on 24 specimens): BL 10.60 mm; HL 3.00 mm (2.41–3.33), HW 2.45 mm (2.22–2.72), ML 2.54 mm (2.24–2.76), HW/HL 0.82, ML/HL 0.85. General colouring dark brown with darker markings, abdomen with a dorsal median stripe with a characteristic pattern ( Fig. 12c ), ventral side paler with dark brown markings; head capsule dark brown, lateral and ventral sides with extensive dark markings ( Fig. 12d ); mandibles dark brown; legs yellowish or whitish; setae of the body black. Head longer than wide; mandibles comparatively strong, shorter than the head capsule ( Fig. 12a ); interdental mandibular setae: (3–4)(1)(1)(0). Pronotum covered by large setae interspersed with short bristles ( Figs. 4C , 12b ). Mesothoracic and abdominal spiracles brown. VIII abdominal sternite with odontoid processes; IX sternite with a ventral pair of spiniform setae and with two small rastra each equipped with 4 sub-equal digging setae ( Figs. 3C , 12e ).

Bio-ecology. D. tetragrammicus is an euryoecious species and its larvae are able to colonize any microhabitat with presence of dry and fine substratum, thus it is very abundant and widespread. In southern Europe it is found from coastal dunes to montane forests, in a large array of habitats, always in dry conditions even if punctiform. The larvae appear avoid exposed sites, preferring protected niches such as at the base of trees or shrubs, under rocks or in their proximity. Therefore they are absent from open coastal sand dunes while they are common on back dunes with conspicuous vegetation growing. D. tetragrammicus larvae are frequent in rocky microhabitat such as escarpments or under overhangs and they are able to colonize similar artificial structures, such as stone walls.

Distribution. Widespread in the western Palaearctic, only avoiding cold climates and true deserts.

Remarks. The larva of D. tetragrammicus differs from D. annulatus , the only other European congener, for its overall dark brown colouring and pattern while D. annulatus is much paler, sand-like in colour, with contrasting dark markings ( Acevedo et al. 2013). The pigmentation pattern of the dorsal side of the abdomen, composed by a median series of contiguous circular markings is a constant character in this species allowing the identification of all larval stages of D. tetragrammicus . Finally, the relatively conspicuous size of this antlion permits an immediate distinction of the 3 rd instar larvae from the other known member of the tribe.

Figures

FIGURE 3. IX and VIII abdominal sternite of 3rd instar larva of Dendroleontini and Nemoleontini. A, Dendroleon pantherinus; B, Nemoleon notatus; C, Distoleon tetragrammicus; D, Creoleon lugdunensis; E, Neuroleon assimilis; F, Macronemurus appendiculatus; G, Megistopus lucasi; H, Gymnocnemia variegata. Scale bar: 1 mm.

FIGURE 4. Pronotum of 3rd instar larvae of Dendroleontini and Nemoleontini; A, Dendroleon pantherinus; B, Nemoleon notatus; C, Distoleon tetragrammicus; D, Creoleon lugdunensis; E, Neuroleon nemausiensis; F, Macronemurus appendiculatus; G, Megistopus lucasi; H, Gymnocnemia variegata. Scale bar: 1 mm.

FIGURE 12. Distoleon tetragrammicus (Fabricius, 1798), 3rd instar larva (France: Gard, Générac). Dorsal (above), ventral (middle) and lateral (below) view; a–e: diagnostic characters, see species description.