page_title: Empis borealis
section_title: Description
hierarchical_section_title: Empis borealis / Description
caption_attribution_description: English: Scandinavia from space in winter. The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA’s Terra satellite captured the above image of the Scandinavian Peninsula on February 19, 2003. With a landscape largely shaped by glaciers over the last ice age, the Scandinavian Peninsula is as picturesque in the winter as it is cold. Along the left side of the peninsula, one can see the jagged inlets, known as fjords, lining Norway’s coast. Many of these fjords are well over 2,000 feet (610 meters) deep and were carved out by extremely heavy, thick glaciers that formed during the last ice age. The glaciers ran off the mountains and scoured troughs into Norway’s coastline with depths that reached well below sea level. When the glaciers melted, the seawater rushed into these deep troughs to form the fjords. The deepest fjord on Norway’s coast, known as Sogn Fjord, lies in southwest Norway and is 4,291 feet (1,308 m) deep. Glaciers also carved the mountains in Norway and northernmost Sweden. South of this mountainous region, however, Sweden consists mostly of flat, heavily forested land dotted with lakes. Lake Vänern and Lake Vättern, the largest of Sweden’s lakes, do not freeze completely during the winter months and can be seen clearly at the bottom of the peninsula. Lake Vättern, the smaller of the two lakes, was connected to the Baltic Sea during the last ice age. After the ice melted, a tremendous weight was lifted off of the peninsula, and the landmass rose up to separate the lake from the Baltic Sea. To the northeast of the peninsula lies Finland with more than 55,000 lakes, most of which were also created by glacial deposits. Español: Escandinavia en invierno, imagen de la NASA Français&#160;: Scandinavie en hiver depuis l'espace. Image prise par l'instrument MODIS à bord du satellite Terra de la NASA. Avec ses paysages sculptés par les glaciers du quaternaire, la Scandinavie en hiver est aussi pittoresque que froide. A l'ouest sont visibles les étroits bras de mer appelés fjords, qui ponctuent la côte norvégienne. Ces fjords très profonds (plus de 600 m et jusque 1308m dans le Sognefjord) ont étés creusés par de lourds glaciers au cours des âges glaciaires. Ces glaciers descendus de la montagne ont creusé leurs vallées bien en dessous du niveau de la mer. A la fin de la glaciation, c'est donc la mer qui a envahis ces profondes vallées. Au sud de ces montagnes, la suède est un pays de plaines couvert de forrêts et de lacs. Les deux plus grans lacsde suède, les lacs Vänern et Vättern, sont aisément visibles au sud car ils ne sont pas pris par les glaces en hiver. Le plus petit des ces deux lacs, le lac Vättern, était une baie de la mer baltique peu après la dernière glaciation. Après la fonte des glaces, et le retrait de leur poid énorme sur la péninsule, celle ci s'est relevée et le lac a été séparé de la mer. Au nord est de la pénisule se trouve la finlande, pays aux 55 000 lacs, souvent d'origine glaciaire. Nederlands: Satellietopname van Noorwegen, Zweden en Finland in de winter Română: Peninsula Sandinavă în timpul iernii — vedere din satelit (19 februarie 2003). Русский: Скандинавский полуостров зимой (19 февраля 2003) Svenska: Satellitbild över Skandinavien. I Norge finns det fjordar, i Sverige sjöar och i Finland också. Hela halvön är täckt av snö på vintern. Även om det är kallt om vintern nu, så var det ännu kallare på istiden.
context_page_description: Empis borealis is a species of dance flies in the fly family Empididae. It is found in most of Europe, except the Balkan Peninsula, the Baltic Region and the Iberian Peninsula. The brown wings of the female are very broad, while the male fly’s wings are narrower.
  This particular species of fly exhibits sex-role reversal in its mating process, with female flies aggregating in swarms to compete for male choice. Female fly swarms change their flying behavior in the presence of males, who present nuptial gifts to females before mating.
context_section_description: E. borealis are empidids, commonly known as dance or balloon flies. Adult E. borealis are small- to medium-sized flies, about 6 to 8 mm long, with dark brown wings. The species exhibits sexual dimorphism in several attributes. Firstly, the fly's wing size depends on whether the fly is male or female. Females have broad wings, about 60% larger than those of the males. Males and females also differ in abdomen tip shape. Females have a pointed tip, while males have a larger tip with a hypopygium, or abdominal segment, that supports the copulatory structure. The species can be easily identified in the field because it is the only empidid species present during May.
  One of the species’ common names is the balloon fly, which refers to the male flies’ practice of bringing nuptial gifts in a woven silk abdominal “balloon” to the females before mating. With their prey caught in these "balloons", male flies approach a swarm of females for mating.
caption: Scandinavia
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