Megistoleon Navás, 1931

Badano, Davide, 2013, Description of Megistoleon thaumatopteryx sp. nov. with notes on the genus Megistoleon Navás (Neuroptera, Myrmeleontidae), Zootaxa 3635 (2), pp. 194-200 : 195

Megistoleon Navás, 1931

Type species: Megistoleon fumosus Navás, 1931 .

Diagnosis. Large antlions but of delicate appearance, with broad wings characterized by conspicuous dark and white markings especially toward the apex, particularly extended in the hind wings. Antennae without apical club, interantennal distance shorter than one and a half of the scape diameter; wings with a particularly dense venation, costal field of forewing mostly biareolated, triareolated in proximity of the pterostigma ; males equipped with pilula axillaris ( Figs 1–2 ).

Redescription. Head with a moderately raised vertex; antennae long, slender and cylindrical without an apical dilatation, close at the base, their reciprocal distance not superior to one and a half of the scape diameter; labial palpi with the last segment only slightly swollen at the base in both sexes. Pronotum wider than long. Legs relatively long and slender, tibial spurs of all legs shorter than the first tarsomere. Wings broad, with very numerous dark crossveins; membranes mostly hyaline with dark markings and large dark soffusions toward the apex, particularly evident in the hind wings; pterostigmata distinct, very large and whitish in color. Forewing with ample costal field, biareolated except at the base, triareolated after the middle of the wing; Rs arising well after Cubital fork; Media posterior situated in close proximity of the cubital fork; anterior and posterior Banksian lines present (see comments). Hind wing with biareolated costal field only immediately before the pterostigma ; 7 presectoral crossveins; Banksian line present (see comments). Hind wings of the males equipped with pilula axillaris. Abdomen elongated, shorter than the wings in both sexes. Male: ectoproct simple, not forcipated; IX sternite triangular; gonarcus arch-like, mediuncus slightly pronounced, parameres in close contact and almost fused. Female: anterior gonapophyses large and rounded, posterior gonapophyses digitiform and longer than the posterior gonapophyses, lateral gonapophyses rounded.

Comments. The genus Megistoleon shows the synapomorphies of the tribe Myrmeleontini : CuP of forewing originates at basal crossvein, forewing vein 2A runs close to 1A for short distance and then bends at sharp angle toward 3A merging with it, Rs arising distal from the base, hind wing with more than 4 presectoral crossveins, basitarsus of hind leg shorter than apical tarsomere (Markl 1954; Stange 2004). The relationships among the members of this tribe are still poorly understood, however this taxon is clearly recognizable thanks to a combination of apomorphic characters. The costal area of the forewing subdivided in two rows of cells for most of its length and three rows near the pterostigma , is an unique character of this genus. The only other genus of Myrmeleontini with triareolated costal area is the peculiar Fijian endemic Dictyoleon Esben-Petersen, 1923 , but occasionally some specimens of Weeleus Navás, 1912 , present this feature as simply a variable characteristic of individual value (New 1982). The above-mentioned genera are clearly separated by overall morphology and they are not closely related among them. Moreover, biareolated costal area in proximity of the pterostigma is present in other Myrmeleontini of conspicuous dimensions: Hagenomyia Banks, 1911 , Baliga Navás, 1912 and in some particularly large species of Myrmeleon Linnaeus, 1767 (once included in Macroleon Banks, 1911 ). Another interesting and distinguishing character in Megistoleon is represented by the short interantennal distance, inferior to one and a half the scape width, while in most representatives of the tribe it is at least as wide as two times the scape width. Even in this case, the character is shared with a stand-alone genus: Porrerus Navás, 1913 , a Neotropical taxon included in a dedicated subtribe (Stange 2004). The members of the genus Megistoleon can show Banksian lines on both pair of wings, however these are not always clearly discernible thus appearing a character of individual value, at least in M. ritsemae .

Figures

FIGURES 1 – 2. Habitus of Megistoleon species. 1. M. ritsemae, male (Cameroon, Mt. Cameroon). 2. M. thaumatopteryx sp. nov., holotypus, female (Mozambique, Sofala prov.), abdomen in situ.