Robust Skimmer. Forse Skepper
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Llarge ( together with O. trinacria the largest in the southern African region), powerfully built, with a green brown mottled aging to pruinescent grey brown thorax and blue pruinescent abdomen with very long slender append.
Key identification features:
- Lenght 50 - 56 - 58mm, wingspan 76 - 83 - 86mm, pterostigmas 2.5 - 4mm
- Face mostly lighter bluish grey. Labium is dull yellow with dark brown central marking not quite reaching anterior margin. Labrum is dull yellow. Anteclypeus, postclypeus and front of frons is light bluish grey, not spectacled. Sides and top of frons adjacent to eyes is dark brown. Head dimpled above, black with two small sharp peaks, without groove.
- Eyes light greenish grey with blackish mottled marking in the lower area.
- Thorax indistinctly marked, light bluish grey on top (brownish green and brown when young), mottled brown and dark brown at sides. With aging, it develops some thin pruinosity, hence appearing mainly brown.
- Wings are clear to slightly smoky. with a small amber patch in hind margin.of hind wing only. 2 cell-rows in radial planate, sum of cell-doublings in all wings 11-29, rarely down to only 4. Pterostigmas yellowish brown with dark brown anterior margins. More than 3 mm and 10% of hindwing length
- Abdomen has well tapered waist. All pale pruinescent blue with possible yellowish brown indistinct markings on the dorsal area when young. Segment 8 - 10 (½ S 8 hind margin) black. Clapers (appendages) black with creamy yellow at the tip of the cercus ( upper clasper).
- Indistinctly marked light and dark brown, wings slightly smoky. 2 yellowish brown stripes either side of thin black stripe on dorsal carina. Foliations small yellowish brown bordered in dark brown.
Similarities with other species:
- In contrast to O. trinacria, O. robustum is robust, not slender and the abdomen is shorter than the hindwing. O. robustum easily distinguished from male O. trinacria by pruinose blue colour.
- Final identification should by by inspection of the secondary genitalia and measurement.
Distribution and habitat:
- Northern KZN coastal area. Visible in Botswana, Namibia, DRC and Zambia but should be visible in Zimbabwe and Mozambique
- Prefers standing and often temporary waters. Marshy verges of pans, lakes, and floodplains, in open landscapes, but sometimes in open areas in forest. Usually with emergent and often aquatic vegetation, often with a soft (like muddy) bottom.
- From 900 to 1500 m above sea level, but near sea level in South Africa.
- Very conspicuous as it perches on reeds and makes short hunting flight before it returns to its perch.