Stenus

Stenus is a genus of semiaquatic rove beetles in the subfamily Steninae, and one of the largest genera in the kingdom Animalia, with some 3100 known species worldwide (only the beetle genus Agrilus is comparable in size). They are predators of Collembola and other small arthropods. Adults have a protrusible labium with a sticky tip used in prey capture. To overcome the rapid escape of Collembola, the labium is protruded at high speed (1-3 ms in Stenus comma) by hemolymph pressure, and immediately withdrawn (withdrawn in 30-40 ms in Stenus comma), pulling the prey within the range of the mandibles. However, the labium tip does not easily stick to prey covered in scales or setae or that have a large body size. Stenus comma is more likely to catch such prey by lunging forward and grabbing them directly with its mandibles rather than using its labium. Stenus species are also known for "skimming" on the water surface using their pygidial gland secretions that act as a surfactant and rapidly propel the beetle fast forward, a phenomenon known as the Marangoni effect. Stenus comma has been seen to achieve a velocity of 0.75 m/s, and to cover a distance of up to 15 m if the secretion is continuous.

==Selected species== Stenus adelops Casey, 1884 Stenus adspector Maklin, 1852 Stenus advena (Casey, 1884) Stenus agnatus (Casey, 1884) Stenus alacer Casey, 1884 Stenus alpicola Fauvel, 1872 Stenus alveolatus Casey, 1884 Stenus amabilis (Casey, 1884) Stenus amicus Casey, 1884 Stenus amplifacatus Benick, 1921 Stenus angustus Casey, 1884 Stenus animatus Casey, 1884 Stenus annularis Erichson, 1840 Stenus arculus Casey, 1840 Stenus argus Gravenhorst, 1806 Stenus arizonae Casey, 1884 Stenus artus Casey, 1884 Stenus austini Casey, 1884 Stenus bakeri Bernhauer, 1910 Stenus biguttatus (Linnaeus, 1758) Stenus bilentigatus Casey, 1884 Stenus bipunctatus Erichson, 1839 Stenus biwenxuani Tang & Li, 2013 Stenus caenicolus Notman, 1919 Stenus californicus Casey, 1884 Stenus callosus Erichson, 1840 Stenus canadensis (Casey, 1884) Stenus canaliculatus Gyllenhal, 1827 Stenus capucinus Boheman, 1858 Stenus cariniceps Maklin, 1852 Stenus carinicollis Casey, 1884 Stenus carolinae Casey, 1884 Stenus carolinus Bernhauer, 1917 Stenus chalybeus Boheman, 1858 Stenus chapini Blackwelder, 1943 Stenus colon Say, 1834 Stenus colonus Erichson, 1840 Stenus comma LeConte 1863 Stenus convictor Casey, 1884 Stenus corvus Casey, 1884 Stenus costalis Casey, 1884 Stenus croceatus (Casey, 1884) Stenus cubanus Blackwelder, 1943 Stenus cubensis Bernhauer, 1910 Stenus curtus Casey, 1884 Stenus delawarensis Casey, 1884 Stenus dispar Casey, 1884 Stenus dissentiens Casey, 1884 Stenus dives Casey, 1884 Stenus dolosus Casey, 1884 Stenus dyeri Blackwelder, 1943 Stenus edax Notman, 1920 Stenus ellipticus Casey, 1884 Stenus eriensis Casey, 1884 Stenus erythropus Melsheimer, 1844 Stenus exasperatus Benick, 1925 Stenus exploratus Fall, 1926 Stenus falli Scheerpeltz, 1933 Stenus femoratus Say, 1834 Stenus flavicornis Erichson, 1840 Stenus floridanus Casey, 1884 Stenus fraternus (Casey, 1884) Stenus frigidus Falls, 1926 Stenus fulvoguttatus Notman, 1920 Stenus gemmeus Casey, 1884 Stenus gibbicollis Sahlberg, 1880 Stenus gilae Casey, 1884 Stenus gratiosus Casey, 1884 Stenus gravidus Casey, 1884 Stenus haitiensis Blackwelder, 1943 Stenus hirsutus Casey, 1884 Stenus hispaniolus Blackwelder, 1943 Stenus hubbardi Casey, 1884 Stenus immarginatus Mäklin, 1853 Stenus incertus Casey, 1884 Stenus incultus Casey, 1884 Stenus indigens Casey, 1884 Stenus ingratus Casey, 1884 Stenus inornatus Casey, 1884 Stenus insignis Casey, 1884 Stenus integer Casey, 1884 Stenus intrusus Casey, 1884 Stenus juno (Paykull, 1789) Stenus juvencus Casey, 1884 Stenus laetulus (Casey, 1884) Stenus leviceps Casey, 1884 Stenus limatulus Benick, 1928 Stenus liupanshanus Tang & Li, 2013 Stenus luctuosus Casey, 1884 Stenus luculentus Casey, 1884 Stenus lugens Casey, 1884 Stenus lutzi Notman, 1920 Stenus maritimus Motschulsky, 1845 Stenus megalops (Casey, 1884) Stenus mendax Casey, 1884 Stenus meridionalis (Casey, 1884) Stenus militaris Casey, 1884 Stenus minor Casey, 1884 Stenus montanus Casey, 1884 Stenus monticola Casey, 1884 Stenus morio Gravenhorst, 1806 Stenus mundulus Casey, 1884 Stenus murphyanus Bernhauer, 1917 Stenus nanus Stephens, 1833 Stenus neglectus Casey, 1884 Stenus nimbosus Casey, 1884 Stenus nitescens (Casey, 1884) Stenus noctivagus Casey, 1884 Stenus obstrusus Casey, 1884 Stenus occidentalis Casey, 1884 Stenus odius Blackwelder, 1943 Stenus pacificus Casey, 1884 Stenus palposus Zetterstedt, 1838 Stenus papagonis (Casey, 1884) Stenus parallelus Casey, 1884 Stenus pauper Casey, 1884 Stenus pauperculus Casey, 1884 Stenus perexilis Notman, 1920 Stenus personatus Benick, 1928 Stenus pertinax (Casey, 1884) Stenus pettiti Casey, 1884 Stenus pinguis (Casey, 1884) Stenus placidus Casey, 1884 Stenus plicipennis (Casey, 1884) Stenus pluto Casey, 1884 Stenus pollens (Casey, 1884) Stenus pterobrachys Gemminger & Harold, 1868 Stenus pudicus Casey, 1884 Stenus pugetensis Casey, 1884 Stenus pumilio Erichson, 1839 Stenus punctatus Erichson, 1840 Stenus punctiger Casey, 1884 Stenus ranops Casey, 1884 Stenus renifer LeConte, 1863 Stenus retrusus (Casey, 1884) Stenus rugifer Casey, 1884 Stenus sayi (Casey, 1884) Stenus scabiosus Casey, 1884 Stenus schwarzi Casey, 1884 Stenus sculptilis Casey, 1884 Stenus sectator Casey, 1884 Stenus sectilifer Casey, 1884 Stenus semicolon LeConte, 1863 Stenus shoshonis Casey, 1884 Stenus similiatus Blatchley, 1910 Stenus simplex Casey, 1884 Stenus solutus Erichson 1840 Stenus sphaerops Casey, 1884 Stenus strangulatus Casey, 1884 Stenus stygicus Say, 1834 Stenus subtilis Casey, 1884 Stenus tacomae Casey, 1884 Stenus tahoensis Casey,1884 Stenus tarsalis Ljungh, 1804 Stenus tenuis Casey, 1884 Stenus terricola Casey, 1884 Stenus teter Notman, 1920 Stenus texanus Casey, 1884 Stenus torus Benick, 1925 Stenus trajectus (Casey, 1884) Stenus tristis Casey, 1884 Stenus tuberculatus Casey, 1884 Stenus utenis Casey, 1884 Stenus vacuus Casey, 1884 Stenus venustus Casey, 1884 Stenus verticosus Casey, 1884 Stenus vespertinus Casey, 1884 Stenus vestalis Casey, 1884 Stenus vexatus Casey, 1884 Stenus vicinus Casey, 1884 Stenus villosus Casey, 1884 Stenus vinnulus Casey, 1884 Stenus vista Sanderson, 1946 Stenus zunicus Casey, 1884