What is the family of this insect caught by my Drosera?
This is a Dark-winged fungus gnat (family Sciaridae); the European species of the family are dealt with by Menzel, F.; Mohrig, W., 1999, Revision der paläarktischen Trauermücken (Diptera, Sciaridae) [A Revision of the Palaearctic Black Fungus Gnats (Diptera: Sciaridae)], Studia Dipterologica Supplement, (6):761 pages; copies are sold by Ampyx-Verlag (see http://www.ampyx-verlag.de/lilac_cms/de/4852,,refz,rd,368,2914,12/index.html).  Some species of the family have economic importance, but identification to species usually requires male specimens which must be at least temporarily mounted on microscope slides.