Blue Cascader Blouklatertjie
Zygonyx natalensis (Martin, 1900)
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Key identification features:
- When young blue yellow and brown becoming pruinesant grey and brown
- Face light brown in front, dark metallic blue above. Labrum yellow brown with blackish margin and central dark dimple. Anteclypeus and postclypeus light brown. Frons yellow brown in front, bright metallic blue and dimpled above extending to peaks on top of head.
- Eyes dull turquoise to grey. When young light blue
- Thorax mottled light and dark brown, slightly metallic, with long hairs on top front . Dorsal thorax uniformly blue becoming grey with age. Mature individuals brown and a mottled covering of thin pale blue pruinescence, although overall appearance is one of dark blue, becomes scratched and scuffed with age. Shoulders with long, dense white hairs.
- Wings are clear, becoming smoky with age . Pterostigmas dark yellowish brown, lighter on underside . 9½-11½ Ax in Forewing
- Abdomen blackish brown with straw-coloured streaks becoming dark brown and pruinesant blue with age . Segment 1 to first half of segment 3, and s7- 8 with a thin cover of pale blue pruinescence which creates a dark blue appearance. S4 to 7, s10 and appendages blackish. S7 unmarked, mottled patch on top pruinose, or marked with spots similar to those on preceding segments. S4-7 may flatten and distinctly narrower that the rest of abdomen, with s 7-10 rounded S1-6 with yellow and brown streaks disappearing with age
- More robust, slightly larger than male
- Thorax dark brown. slightly metallic with yellowish to light brown mottled markings
- Wings smoky, particularly with age. Pterostigmas dark yellow brown. Young individuals in the Western Cape with amber leading edge to forewings and small amber patch at base of all wings
- Abdomen dark brown with yellow brown side markings. Segment 7 with fine yellow line along top of first half. Segment 8 also with fine yellow line along top, but shorter and wider, almost spot-like.
Compared with other species:
- Metallic tip of frons and vertex distinguishes Z. natalensis (Blue Cascader) and Z. torridus (Ringed Cascader) from Orthetrum (Skimmers).
- Both Z. natalensis and Z. torridus hunting behaviour of flying rapidly over splash zones are similar, but is unlike any Orthetrum (Skimmer)
- Z. natalensis is similar to but smaller than Z. torridus. Z. torridus is blackish brown with distinct yellow marks on abdomen and lightly pruinescent
- Female Z. natalensis yellow markings make up only a small fraction of the abdominal segments (whereas it is about 50% Z. torridus), Z. natalensis vertex is highly metallic. All brown and only slightly metallic in Z. torridus. The upper corners of Z. natalensis frons are metallic, but yellow in Z. torridus).
Distribution and habitat:
- KZN, MP Western and Eastern areas), LP. Localized in WCP and ECP
- Rivers and streams in open landscapes, but sometimes in open areas in forest or shaded by gallery forest. Especially faster sections (rapids, falls), usually with rocks.
- From 0 to 2200 m above sea level, but mostly below 1900.
- It hawks among bushes and trees away from water. It flies rapidly up and down faster sections (rapids, falls) of streams, usually with rocks, and hovers low over riffles and splash zones