Sphex gracilis, Doerfel, Thorleif H. & Ohl, Michael, 2015

Doerfel, Thorleif H. & Ohl, Michael, 2015, A revision of the Australian digger wasps in the genus Sphex (Hymenoptera, Sphecidae), ZooKeys 521, pp. 1-104 : 30-33

Taxon classification Animalia Hymenoptera Sphecidae

Sphex gracilis sp. n.

Material examined.

Holotype. ♂, AUSTRALIA:NSW: 35 km N of Menindee, 26.11.1988, N. W. Rodd (AMS). Paratypes. AUSTRALIA:NSW: Broken Hill, 1♂, 15.02.1942, C. E. Chadwick (AMS); 40 km W of Cobar, 3♂, 12.11.1985, N. W. Rodd (AMS); 30 km N of Euston, 1♀, 28.11.1988, N. W. Rodd (AMS); Fowlers Gap, 114 km SW of Broken Hill, Barrier Range, 2♂, 21.12.1988, G. J. & R. L. Langston (CAS); Gilgandra, 4♀, 1♂, Nov-Dec 1986, G. A. Holloway (AMS); 40 km E of Gol Gol, 1♂, 27.11.1992, N. W. Rodd (AMS); Lightning Ridge, 1♂, 14.10.1989, I. D. Buddle (AMS); 20 km N of Menindee, 1♀, 10.11.1985, N. W. Rodd (AMS), 35 km N of Menindee, 2♂, 26.11.1988, N. W. Rodd (AMS); Pooncarie, 1♂, 27.11.1991, N. W. Rodd (AMS), 3♀, 28.11.1992, N. W. Rodd (AMS); 112 km N of Wentworth, 1♂, 28.11.1991, N. W. Rodd (AMS); 15 km E of Hillston, 1♀, 29.11.1988, N. W. Rodd (AMS); SA: Calperum Station 16 km N Renmark, 34°02.9'S, 140°42.2'E, 1♀, 03.12.2010, V. Ahrens & W. J. Pulawski (CAS), 1♂, 04.12.2010, V. Ahrens & W. J. Pulawski (CAS); 17 km E of Renmark, 1♀, 23.11.1977, D. K. McAlpine & M. A. Schneider (AMS); 3 km N Renmark, 34°09.5'S, 140°44.2'E, 1♂, 02.12.2010, V. Ahrens & W. J. Pulawski (CAS).

Diagnosis.

This species differs from other Australian Sphex of the Sphex resplendens group in having a combination of the following features: erect setae on clypeus uniformly silvery-white, metasoma black, and clypeal surface without wrinkles. Further more, the metasoma of female Sphex gracilis is considerably slenderer than that of other examined species (Fig. 18A).

Description.

Body black. Wing membrane hyaline, with fuscous band at apex. Wing veins orange to light brown. Appressed pubescence and erect setae on clypeus and frons silvery. Pubescence on mesosoma silvery-white. Scutellum with shallow medial impression. Pubescence on propodeal enclosure short and sparse, leaving sculpture easily visible.

Female: Body length 19.9-25.9 mm. Mandible basally and ventral part of clypeus reddish, distal tarsomeres sometimes inconspicuously orange. Wing veins darker near apex. Forebasitarsal rake with 5-8 spines which are markedly short and stout. Free clypeal margin faintly convex medially. Clypeus mostly glabrous, only laterally with pubescence. Distance between hind- ocelli equal to their shortest distance to compound eyes. Pubescence on scutum denser laterally and posteriorly. Scutellum flat. Length of petiole nearly equal to flagellomere II. Tomentum very sparse on metasomal tergum I, absent on tergum II.

Male: Body length 18.5-20.6 mm. Forewing membrane sometimes with yellow tinge, hindwing membrane entirely hyaline. Wing veins light brown, sometimes orange, often darker near apex, sometimes uniformly colored. Free clypeal margin simple, concave towards center. Clypeus with narrow medial glabrous stripe, ventral part also glabrous. Distance between hind- ocelli 0.9 × their shortest distance to compound eyes. Pubescence on scutum denser laterally. Scutellum convex. Length of petiole 1.4 × length of flagellomere II. Tomentum dense on metasomal tergum I, moderately dense on tergum II. Metasomal tergum V and VI with few bristles. Metasomal sterna II–VI mostly glabrous, apical margin of metasomal sternum VII and VIII covered with silvery pubescence. Metasomal sternum VIII entire, its lateral margin inconspicuously concave.

Discussion.

At first, the males and females of this species look quite different. While the habitus of the male matches that of most examined species of Sphex , the female’s metasoma is much slenderer and seems longer than that of other species. Nonetheless, they most likely are the same species, as indicated by the following features.

One of the most important characters that connect both sexes is the uniformly silvery pubescence on the clypeus. In at least six of the ten other Australian species in the Sphex resplendens group, the erect setae on the clypeus are black. Of the remaining four species, two are colored bright orange. One of the other two has extremely unusual structures on the clypeal surface. Concerning the last remaining species other than Sphex gracilis , male and female individuals were found that have both silvery and golden pubescence on the clypeus as well as on the propodeum, a unique trait among the studied material.

Moreover, this is also the only species in the Sphex resplendens group where some males and females (see below for explanation) have the wing membrane entirely hyaline (excluding the apical margin), even at the base, and without any yellow. Both also have a very similar sculpture on the propodeal enclosure, and they also share the same length, density and orientation of its pubescence. Finally, the collecting localities show that both sexes occur in close proximity (Fig. 18E).

There seems to be some variability among individuals, but they are nonetheless presumed to be of a single species. In both sexes, there are specimens that come from the same collecting series and are distinctively different in their wing coloration. One group possesses brown wing veins and wings that have no hint of yellow (Fig. 18C), the other group has orange wing veins and (in males) a yellow tinge in the basal half of the forewing membrane (Fig. 18D).

Etymology.

Gracilis is a Latin adjective meaning “slender”. It refers to the habitus of the female metasoma.