Libelloides Schäffer, 1763

Badano, Davide & Pantaleoni, Roberto Antonio, 2014, The Larvae of European Ascalaphidae (Neuroptera), Zootaxa 3796 (2), pp. 287-319 : 304

Libelloides Schäffer, 1763

Diagnosis. Head capsule dilated posteriorly, dorsal side with a pronounced posterior depression; antennae thin, longer than the ocular tubercles; ocular tubercles cylindrical; mandibles armed with three teeth, the median tooth is the largest and closer to the apical tooth than to basal tooth; mandibles equipped with interdental pseudo-teeth; labial palpi four-articulated, segments 2-4 thin, longer than the basal width of the mandible; mesothorax bearing two sub-equal pairs of cylindrical scolus-like processes; metathorax provided with a large anterior pair of scoluslike processes followed by a posterior pair half the size of the previous ones; first pair of abdominal spiracles placed on the lateral sides; abdomen with eight pairs of dorsal cylindrical scolus-like processes, ventral series formed by two pairs of scolus-like processes on the first two anterior segments and very short tubercle-like processes on the following six segments; VIII sternite with short odontoid processes bearing dolichasters; IX sternite with two short rastra each bearing four digging setae ( Figs. 1D , 2E ); body covered with short goblet-shaped dolichasters and stick-shaped ones ( Fig. 3E ).

Examined species. L. coccajus (Denis et Schiffermüller, 1775) , L. latinus (Lefèbvre, 1842) , L. longicornis (Linnaeus, 1764) , L. macaronius (Scopoli, 1763) , L. ictericus (Charpentier, 1825) , L. siculus (Angelini, 1827) , L. corsicus (Rambur, 1842) .

Comments. The genus Libelloides is a characteristic faunal element of the Palaearctic region. Despite the status of some taxa needs to be evaluated, Libelloides includes at least 19 species of which about 12 are present in Europe, mainly in the western Mediterranean area (H. Aspöck et al. 2001). The larval morphology and ecology of this genus are poorly known: the first accurate study on this subject was realized by Brauer (1854) while the genus characters of the larvae were defined by Hagen (1873). Notably only two recent comparative works on this subject exist ( Rousset 1973; Pieper & Willmann 1980). The larvae of L. cunii (Selys-Longchamps, 1840) , L. lacteus (Brullé, 1832) and L. rhomboideus (Schneider, 1845) are actually known ( van der Weele 1909; Navás 1915; Pieper & Willmann 1980) but their descriptions are excessively concise or referring to not diagnostic instars, for this reason adequate comparisons are not normally possible with the exception of L. lacteus , tentatively inserted in the key. Furthermore, Navás (1915) described a larva as L. hispanicus (Rambur, 1842) , but this identification appears questionable.

Remarks. The larvae of the different species of Libelloides show a noticeable overlapping in the macroscopic characters normally used for identification purposes, such as: chaetotaxy, morphometry and the general pigmentation pattern. The relative difficulty to find the larvae in the field and their camouflaging behaviour make these light differences even more unsuitable. In particular, their camouflage is so effective that the different species are not recognizable if not artificially cleaned making visible the pigmentation pattern.

Figures

FIGURE 1. Taxonomic characters of Ascalaphidae larvae. A, Deleproctophylla australis dorsal and ventral view; B, head of Ascalaphus festivus; C, head of Puer maculatus; D, VIII and IX sternites of Libelloides siculus.

FIGURE 2. VIII and IX abdominal sternites of 3rd instar larva of Ascalaphidae. A, Ascalaphus festivus; B, Bubopsis agrionoides; C, Puer maculatus; D, Deleproctophylla australis; E, Libelloides macaronius. Scale bar: 1 mm.

FIGURE 3. Chaetotaxy of the VIII abdominal sternite of 3rd instar larva of Ascalaphidae. A, Ascalaphus festivus; B, Bubopsis agrionoides; C, Puer maculatus; D, Deleproctophylla australis; E, Libelloides longicornis. Scale bar: 100 µm.