Berothidae

Wedmann, Sonja, Makarkin, Vladimir N., Weiterschan, Thomas & Hörnschemeyer, Thomas, 2013, First fossil larvae of Berothidae (Neuroptera) from Baltic amber, with notes on the biology and termitophily of the family, Zootaxa 3716 (2), pp. 236-258 : 240-243

Berothidae indet., larva B

Figs. 3–5

Material examined. Specimen No. 1555 in the private collection of Thomas Weiterschan (Höchst Odw, Germany); a larva in a small piece of Baltic amber (precise collecting locality is unknown).

Description. First instar larva preserved in slightly curved position, ca. 2.25 mm long (including mouthparts), slender.

Head capsule elongate, 0.28 mm long, 0.2 mm wide (length/width ratio 1.4). Stemmata present, but not very clearly visible; probably one on each side (alternatively, a group of 2–3 very small stemmata located close to each other on each side). Dorsally, ecdysial cleavage lines clearly visible consisting of frontal, lateral and coronal sutures. Two anterior arms of frontal suture extending for nearly two thirds of head capsule length, slightly convergent, from inner margin of antennal tubercles to lateral sutures, posterior arms of frontal suture (after joining lateral suture) rather strongly convergent until they touch. Lateral sutures straight, reaching lateral margins of head (in dorsal view), inclined to anterior part of frontal sutures at obtuse angle. Coronal suture rather long ( Fig. 5 B). Of dorsal setae, sockets of lateral clypeal (trichobothrian) seta clearly visible, and probably S7, S5 detected. Ventrally, coxopodites of maxillae (stipes and cardo) and labium clearly distinguished. Stipes and cardo narrow; boundary between them not clearly visible. Labium composed of prementum and postmentum. Prementum short and broad (nearly quadratic, 0.06 mm long); anterior excision not detected; postmentum long and broad, nearly parallel-sided, somewhat broadened in distal portion ( Fig. 5 A).

Mandibles 0.24 mm long, slender, apically pointed. Shape of maxillary blades not clearly visible; these closely associated with mandibles to form mandibulomaxillary stilets.

Antennal sockets located on high projections (antennal tubercles); left antennal tubercle obliquely directed to outside as if following antennal movement. Antennae 3-segmented, longer than mouthparts. Basal segment slightly conical, 0.04 mm long and 0.03 mm wide; second segment elongate, 0.18 mm long, clearly annulated, with distinct contraction in middle and dilated in distal half; third segment very thin, 0.1 mm long, less than 0.01 mm wide, annulated; terminal filiform seta about 0.1 mm long.

Labial palps slightly shorter than mandibulomaxillary stilet, 4-segmented. Basal segment cylindrical, 0.03 mm long; second segment elongate, widest at 2/3 of its length, 0.08 mm long (both ca. 0.02 mm maximum wide); third segment cylindrical, 0.03 mm long and half as wide as 2nd segment; fourth segment 0.07 mm long and basally slightly thinner than third segment, gradually thinned towards rather pointed apex. Second to fourth segments annulated.

Cervix 0.18 mm wide, probably partially retracted into prothorax; visible length 0.02 mm dorsally, 0.08 mm laterally and ventrally.

Prothorax 0.23 mm long, 0.23 mm wide; two large sclerites indistinct. Mesothorax and metathorax both ca. 0.14 mm long, 0.26 mm wide; both with pair of distinct oval sclerites.

Legs moderately stout; coxa rather long, stout; trochanter very distinct, rather long; femur elongate, stout; tibia short, stout; tarsus very long; pretarsus bearing two short claws and relatively short trumpet-shaped empodium ( Fig. 5 C).

Abdomen divided into 10 segments, nine of which have lateral lobes. Basal segments 1 to 4 short, each ca. 0.07 mm long, ca. 0.25 mm wide; distal segments 5 to 10 gradually becoming narrower, from 0.24 mm (segment 5) to 0.07 mm (segment 10); segments 6 to 8 each ca. 0.15 mm long; segment 5 somewhat shorter; segment 9 0.1 mm long; segment 10 0.08 mm long, and caudal sucker 0.05 mm long ( Figs. 4 C, 5D). Segment 8 with two dorsal trichobothrian sensillae ( Fig. 5 D).

Remarks. Judged from its size, the larva is a first instar. The terminal segments of this larva are fully extended, and its 10th segment is terminated by a caudal sucker. Hitherto, the caudal sucker of the first instar larvae in extant berothid species has never been figured (e.g., Tillyard 1916: Fig. 32; Minter 1990: Figs. 5 , 14; Möller et al. 2006: Figs. 12, 13), although its presence in larvae of this age was mentioned at least in Lomamyia occidentalis (Banks in Baker, 1905) and L. hamata (Walker, 1853) (Toschi 1964; Brushwein 1987). The caudal sucker of larva B is similar to that of the 3rd instar of Podallea vasseana (Navás, 1910) (see Möller et al. 2006: Fig. 35). Usually, the caudal sucker is invaginated and externally not visible (as in the case of the larva A; see Möller 2003: Fig. 43). Interestingly, the sucker is not used when the first instar larva runs (Toschi 1964; Brushwein 1987).

Figures

FIGURE 3. Berothidae indet., larva B, whole larva as preserved. A, photograph. B, drawing (both dorsal view). Scale bar is 0.5 mm.

FIGURE 4. Berothidae indet., larva B. A, head, dorsal view. B, head, ventral view. C, apex of abdomen, dorsal view. Scale bars are 0.1 mm.

FIGURE 5. Berothidae indet., larva B, drawings of body details. A, head, ventral view. B, head, dorsal view. C, right foreleg, ventral view. D, apex of abdomen, dorsal view. an, antenna; cd, cardo; cvx, cervix; cs, coronal suture; cx, coxa; fm, femur; fs, frontal suture; lcs, lateral clypeal seta; lp, labial palpus; ls, lateral suture; md, mandible; mx, maxillary blade; prm, prementum; psm, postmentum; pt, pretarsus; S 5, S 7, head seta; st, stipes; su, caudal sucker; tb, tibia; tr, trochanter; trb, trichobothria; ts, tarsus; VIII to X, 8 th to 10 th abdominal segments. Scale bars are 0.1 mm.