Ranatra, Fabricius, 1790

I know troublingly little about the group here, even less than is hinted at by my only listing the genus.

So, in the absence of anything to say about it, here's a picture:

And now, to put said picture in context:

 - Eukaryota
   - Animalia
     - Eumetazoa
       - Bilateralia
         - Nephrozoa - see also Thelotornis capensis, Lygodactylus capensis, Chalcophaps indica, Sterna hirundo, Ardea goliath, Trachylepis varia and Hipposideros vittatus.
           - Protostomia
             - Ecdysozoa
               - Arthropoda - see also Ligia oceanica, Dicranopalpus ramosus, Argiope bruennichi, Enoplognatha ovata and Hyllus argyrotoxus.
                 - Hexapoda
                   - Insecta
                     - Dicondylia
                       - Pterygota
                         - Manopterygota - see also Pseudagrion hageni and Enallagma cyathigerum.
                           - Neoptera - see also Cyathosternum prehensile, Stictogryllacris punctata, and Sybilla.
                             - Eumetabola - see also Vespula germanica, Synagris proserpina, Astata tropicalis, Senaspis haemorrhoa, Malachius bipustulatus, Otiorhynchus atroapterus, Melolontha melolontha, Anthia fornasinii, Demetrias atricapillus, Helophus pendulus, Episyrphus balteatus, Diasemopsis meigenii, Megistocera filipes, Panorpa germanica, Acada biseriata, Anthocharis cardamines, Laelia robusta, Zebronia phenice and Hagenomyia tristis.
                               - Paraneoptera
                                 - Condylognatha
                                   - Hemiptera
                                     - Heteroptera - see also Anoplocnemis curvipes and Pephricus.
                                       - Nepomorpha
                                         - Nepidae
                                           - Ranatrinae

Ranatra

Fabricius, 1790

Ranatra comprises a species-rich and near-cosmopolitan assemblage of long, slender water scorpions, also known as water-stick-insects to reflect their body-plan, (but only distantly related to true stick insects, which group with the grasshoppers. Traditional, more scorpion-y water-scorpions are usually more leaf-shaped, and are held in the subfamily Nepinae. 

It's worth noting that no water scorpions are venomous - they are all quite harmless true bugs, whose flimsy, pincer-like front legs are for grabbing small aquatic animals, and whose long thin tails are not tails at all but breathing tubes. If you were tadpole-sized, it would be worth treating them with extreme caution, but if you're reading this, you're probably a good deal bigger. 

Being insects, they're also not particularly close to scorpions, which group with spiders and harvestmen in the Arachnida.  

Here's another - more informative, but less appealing to my eye - angle on this particular individual from Chongwe, Lusaka, Zambia, taken in October 2011: