Stenoleon Tillyard, 1916

Miller, Robert B. & Stange, Lionel A., 2012, The cave mouth antlions of Australia (Neuroptera: Myrmeleontidae), Insecta Mundi 2012 (250), pp. 1-65 : 25-26

Stenoleon Tillyard

Stenoleon Tillyard 1916: 60 . Type species: Stenoleon fieldi Tillyard , by original designation.

Further description: New 1985c: 15.

Diagnosis. Adult: antenna long to very long with club absent or greatly reduced; tibial spurs present; female anterior gonapophyses absent, posterior gonapophyses long, often slender; male sternite IX simple rounded; male gonarcus broad and short, parameres platelike, angled anteriorly; male ectoproct without postventral lobe..

Description. Adult: body 20 to 24 mm, forewing 20 to 25 mm, hindwing 19 to 25 mm. Coloration: body dark brown. Structure: antennal club weakly developed at most, about twice the diameter of preceding antennal flagellomeres; ocular rim with short setae that project over eye; tibial spurs well developed; pretarsal claws can not close against ventral setae of distal tarsomere, not one-half length of distal tarsomere; Miller’s organ absent on sternite I; hindleg about as long as foreleg; female anterior gonapophysis absent; forewing slightly longer than hindwing; posterior gonapophysis long, usually slen- der, pregenital plate small, membrane below tergite VIII with distinct sclerotized bars; male sternite IX simple, rounded; gonarcus very broad and short; parameres plate-like, angled anteriorly.

Larva: head capsule about 1.5 times longer than greatest width as viewed dorsally, without dolichasters; antenna about as long as width of head capsule; labial palpus longer than base of mandible; mandible with three equally space teeth gradually increasing in length distally; distance between teeth about one-half distance from mandibular base to basal tooth and about equal to distance between distal tooth and apex; mesothoracic spiracle borne on short tubercle, much wider than long; abdominal spiracles not borne on tubercles; sternite VIII without submedial tooth near posterior margin; sternite IX about as wide posteriorly as length of sternite, set of 4 short digging setae posteriorly.

Distribution. Only Australia.

Biology. The larvae may be found in Zone 1 which is made up of substrate originating in the cave or rock overhang and is exposed to the sun, high temperatures, and rainfall. Species in this zone can handle outside conditions, but may prefer the specialized substrate originating from the cave. They mostly occurred in Zone 2A which has rainfall protection and is cooler than Zone 1 but warmer than other Zones. Also, there is dust or loose material laying over a hard surface but shallow enough to allow the larvae to be covered with their legs anchored. They live in either organic (bat guano powder) or inorganic matter (white calcium powder).

Discussion. New (1985c: 15) referred six species to this genus. However, our studies indicate that the small species of Stenoleon with short, clubbed antennae ( S. gradostriatus New, S. copleyensis New, S. grandithecus New, and S. navasi New) belong to Bandidus Navás and Stenoleon is restricted to the large species ( S. fieldi Tillyard , S. cingulatus New, and a new species) which have very elongate and often filamentous antennae as well as much smaller pretarsal claws. All of the larger species with the elongate antennae inhabit cave mouths or rock overhangs. Thus, the small species of Stenoleon are here transferred to Bandidus Navás with the following new combinations: B. gradostriatus (New) , B. copleyensis (New) , B. grandithecus (New) , and B. navasi (New) .

The larvae of the now restricted Stenoleon have the longest antennae discovered thus far of all the described larval Myrmeleontidae . The larvae are very similar to those of Xantholeon but live in the more light intense Zones 1 and 2A. The pale larva produces a dark colored adult. The major diagnostic character of Stenoleon larvae is the very elongate antenna (longer than head width, Figures 83, 85). Although the larval antenna of S. cingulatus is the same as in S. fieldi , it remains to be seen if the larval antenna of S. xanthopus is equally long since the adult antenna is not as long and filamentous as in the other two species. Unfortunately, the larval antennae are broken off in the larval exuviae found in the cocoons. Adult Stenoleon differ from Xantholeon in having forewing vein CuP originating slightly distal of M-Cu, forewing vein 2A bending at a sharp angle toward 3A (evenly curved in some Xantholeon ), in having many long, erect white bristles on the mesoscutum, the forefemur is beset with many long bristles, narrower wings and smaller eyes.