Horn flies

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Horn flies
Anticheta brevipennis

Anticheta brevipennis

Systematics
Class : Insects (Insecta)
Order : Fly (Diptera)
Subordination : Flies (Brachycera)
Partial order : Muscomorpha
Superfamily : Sciomyzoidea
Family : Horn flies
Scientific name
Sciomyzidae
Fallén , 1820
Mottled snail fly ( Coremacera marginata )
Pherbellia annulipes on dead wood (video, approx. One minute)
Larva of an aquatic horn fly larva. The head capsule pointing downwards, the rear end with appendages between the breathing openings at the top.

The horn flies (Sciomyzidae) are a family of small to medium-sized flies (Brachycera) that are represented worldwide. The larvae of the flies feed mainly on snails as parasites , scavengers or predators . In addition to the common name Marshflies , they are therefore also called Snail-killing Flies in English .

features

In the adult stage, horn flies reach 2 to 14 millimeters in length, depending on the species. The larva of Salticella stuckenbergi from the subfamily Salticellinae becomes over 23 millimeters long in the third larval stage and is thus the largest larva within the horned fly family.

The build of the adult flies is slim, the color is dull gray, rarely glossy black, brown or reddish brown. The legs can be colored red or yellow. The wings are hyaline or have black spots or a network drawing. This striking wing pattern is not a feature of family relationships, although it is not very variable within a species. In many genera only a few species have conspicuous wing markings, the others do not. The costalader is not interrupted, the subcosta is complete. A medio-cubital transverse artery (bm-cu) is present, the anal cell is closed.

The head is hemispherical or round. The antennae are elongated, the arista is often downy hairy, sometimes it also has longer hair. Pointed eyes and ocellated bristles are present, except for the genus Sepedon . There are no vibrissae . The head has large compound eyes .

Way of life

Adult horn flies

The adult horn flies are mostly found in the vicinity of wetlands . Mollusks live here and the larvae can feed on them. The sexually mature animals usually sit in the vegetation on the underside of the leaves and feed on dew and nectar .

Larval development

The larvae of the flies need animal food for their development. The vast majority of larvae attack snails. Some species act as scavengers in the first larval stage, later as parasitoid and in the third larval stage are predatory.

The larvae of the subfamily Phaeomyiinae are parasites or parasitoids of bipedos (diplopods), while the larvae of the other horned flies feed on molluscs or - in rare cases - on annelworms in fresh water .

Annular worms only attack the larvae of the species Dictya disjuncta , Sepedonella nana , Sepedon knutsoni and Sepedon ruficeps . Sepedonella nana from tropical Africa feeds exclusively on the leguminous worm Aulophorus furcatus from the Naididae family . Sepedon ruficeps actually specializes in freshwater snails, but occasionally feeds on the worms.

The larvae of Eulimnia philpotti , Ilione lineata and four species of the genus Renocera , including Renocera pallida, attack mussels. In contrast to certain water bugs , which, as ectoparasites, sometimes also suckle on mussels, these horn fly larvae live as obligatory parasitoids within the mussel shells, at least in the early stages, and some also pupate there. With the exception of Renocera pallida , all species remain under water during this phase of their larval development.

Five species of the genus Anticheta feed exclusively on snail eggs in their early larval stage. Two species stay with this diet in the later larval stages, the others prey on and then also eat the young snails.

All other species attack snails. Most species develop into shell snails , but some species prefer nudibranchs . Both land and water snails are attacked. With a few exceptions, the water snails in question live in fresh water and do not have a lid . In the brackish and salt water area , periwinkles can become food for the larvae of horn flies, but few species are suitable for this.

The female horn flies lay their eggs on or near snails. The larvae of most species first have to find their food source. Some species begin their life cycle as scavengers. The larvae are aquatic or semi-aquatic as well as purely terrestrial . Only larvae that parasitize on mussels can breathe underwater. Terrestrial species are often parasitoids . After the death of their host animal, they crawl out of the snail and live through their final larval stage as snail predators. Some species complete their life cycle in the snail and pupate in the snail shell .

distribution

Species from the horned fly family are found in all biogeographical regions and eco-zones . Oceania with four species, Australia with 12 species and New Zealand with 25 species have the lowest number of species. In the Nearctic , however, there are 172 species, in the Palearctic 157. For the Neotropic there are 91 additional species, for the Afrotropic and Oriental 95 species.

habitat

The habitats of the sexually mature horn flies are mostly on the edge of water and in wetlands . Not only the wetlands themselves form the habitat for the horn flies, forests and meadows are also possible depending on the species. For example, some Pherbellia species, Renocera stroblii and some other species are often found on the shady banks of forest streams. But there are also species that can be found in particularly dry, lime-rich meadows. In subalpine Hochstaudenfluren example, flying the rare Ectinocera borealis . So far, Euthycera alpina has only been found in the Austrian Alps .

Many species live in swamps with a high proportion of sedges . In Europe these are representatives of the genera Ilione , Elgiva and Renocera (e.g. Renocera pallida ). On rushes , especially on Juncus groves, Pherbellia species occur regularly in Central Europe , e.g. B. Pherbellia silana or Pherbellia ventralis . Some other species of the genus Pherbellia can be found on dead wood, e.g. B. Pherbellia scutellaris , Pherbellia rozkosnyi , Pherebellia steyskali or Pherbellia anullipes .

research

The life cycle of many species of horned flies has been deciphered and their reproduction and nutrition have been studied in the laboratory . The reason for this is the function of these flies in regulating the population density of snails. Since some snail species are known as intermediate hosts of human and animal parasites or cause damage in agriculture, the use of horn flies for biological pest control was investigated. However, breeding these flies is difficult and the degree of parasitization is not very high, so that the success of this method does not appear certain.

Another interest of the research lies in the variety of combinations in the food acquisition of the larvae, in which facultative phases alternate with obligatory phases as scavengers, predators, parasites and parasitoids. The evolution of food acquisition and the life cycles of animals are examined for their suitability for clarifying phylogenetic and family relationships.

In regional field research, it is primarily the conspicuous shapes that are collected and recorded, be it because of their patterned wings or because of their considerable size for two-winged people. The smaller species are often overlooked, especially since they are often found in inaccessible wetlands. As a rule, the flies are cremated from the vegetation with the insect net . Adults are often found in light traps as by-catches of butterflies , but these catches are rarely scientifically evaluated.

Systematics

Internal system

The system of horn flies has been fundamentally revised in the past decades, not least due to phylogenetic studies. The groups of Huttonininae , Phaeomyiinae and Tetanocerini used to be regarded as separate families. The Phaeomyiinae differ from the subfamily Sciomyzinae mainly in their way of life, they do not parasitize molluscs, but bipods (Diplopoda). Like the Huttonininae, they are a species-poor group that is sometimes temporarily placed with the horned flies, in other cases listed as a separate family. However, the Tetanocerini are even regarded in more recent systematic studies as part of the subfamily Sciomyzinae, i.e. the horn flies in the narrower sense. You get the rank of a tribe within this subfamily. Whether a separate subfamily is necessary for the Salticellinae with only two recent species or whether a separate tribe or even subfamily should be set up for the approximately 80 species of the genus Sepedon together with related genera, is the subject of further phylogenetic studies. The Helosciomyzidae , which used to be part of the horned fly family, were spun off as an independent family.

Subfamilies

There are different systematic subdivisions of the hornfly family. Around 550 species from 63 genera have been described worldwide, in Europe there are around 150 species from 25 genera from the list given here.

Subfamilies and selected genera
  • Subfamily Huttonininae
    • Tribe Huttoninini
      • Genus Huttonina Tonnoir & Malloch , 1928
        • Subgenus Huttonina Tonnoir & Malloch , 1928
        • Subgenus Huttoninella Barnes & Knutson , 1989
    • Tribe Prosochaetini

Individual evidence

  1. ^ A b c Lloyd Vernon Knutson & Jean-Claude Vala: Biology of Snail-killing Sciomycidae Flies. Cambridge University Press, 2011
  2. ↑ Jean-Claude Vala & Louis Ghélus Gbedjissi: Biology of the Afrotropical Sepedonella nana (Diptera: Sciomyzidae), whose larvae feed only on freshwater Aulophorus furcatus (Oligochaeta: Naididae). Zootaxa, 3102, pages 50-68, 2011
  3. ^ BA Foote, LV Knutson & JB Keiper: The snail-killing flies of Alaska (Diptera: Sciomyzidae) . Insecta Mundi, 326, 13, 1-2, 45, 1999
  4. ^ Jean-Claude Vala et al .: A cornucopia for Sciomycidae (Diptera) . Studia dipterologica, 19, 1/2, pages 67-137, 2012
  5. ↑ Bernhard Merz & Alois Kofler: On the occurrence of horn flies in East Tyrol and Carinthia (Austria) (Diptera: Phaeomyiidae & Sciomyzidae). Reports of the natural science-medical association in Innsbruck, 93, pages 107-119, 2006

literature

  • Lloyd Vernon Knutson & Jean-Claude Vala: Biology of Snail-killing Sciomycidae Flies. Cambridge University Press, 2011 ISBN 0-521-86785-1
  • CO Berg & Lloyd V. Knutson: Biology and Systematics of the Sciomyzidae. Annual Review of Entomology, 23, pp. 239-258, 1978
  • William L. Murphy, Lloyd V. Knutson, Eric G. Chapman, Rory J. Mc Donnell, Christopher D. Williams, Benjamin A. Foote & Jean-Claude Vala: Key Aspects of the Biology of Snail-Killing Sciomyzidae Flies. Annual Review of Entomology, 57, pp. 425-447, 2012

Web links

Commons : Hornfliegen (Sciomyzidae)  - Collection of images, videos and audio files