The biting midges (family Ceratopogonidae) is one of the most species rich amongst the biting flies (Diptera) and has been recorded from most parts of the world. The species are mostly known for their capability to act as vectors for several important diseases, which have helped in shaping the focus to one of its genera, Culicoides Latreille, 1809.   This thesis gives an overview of the knowledge of the Swedish diversity, in the first paper (paper I) with a closer look at the species of Dasyhelea Kieffer, 1911 where all twenty species found in Sweden are presented with their associated localities, and two new species are described.  In the second paper (paper II) the biting midge diversity of Sweden is presented based on specimens collected from several localities. All these individuals were barcoded using the mitochondrial cytochrome oxidase I gene (COI). The analysis included 773 specimens that were assigned into 214 barcoding clusters (BINs) and sorted into 164 groups based on their morphology. The third paper (paper III) broadens the scale were the evolutionary relationships within the family are investigated by applying five protein coding genes (COI, CAD, TPI, AATS and PGD) and specimens from different parts of the World. The analysis recovers Ceratopogonini, Forcipomyia Meigen, 1818 and Bezzia Kieffer, 1899 as paraphyletic and Palpomyia Meigen, 1818 polyphyletic. In the last and fourth paper (paper IV) the family is used as a model organism together with Hymenoptera for an alternative analysis method for reducing the impact of saturation and long-branch attraction using non-synonymous coding (e.g. Degen1) on only parts of a dataset. The effectiveness of the method is compared to the removal of the faster evolving third codon position. The result yields a higher number of supported nodes as well as a higher median of support for the method as well as an ability to reduce long-branch attraction artifacts. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p><p> </p>