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Flies are a vital part of the ecosystem – they provide food for other animals, pollinate plants and recycle organic waste. The potential of these lowly but vital insects has been known for some time and a number of species are already being reared commercially.
Their use in Europe is growing after an EU Regulation was passed in 2017 permitting the use of insect proteins from several fly species – including the black soldier fly and housefly – as feed in aquaculture. Flies already provide a protein source in some pet foods and could soon be used to feed poultry and pigs.
The EU-funded FLYHIGH project has provided new knowledge about the make-up and life cycles of certain fly species. One key task was to explore the genetic diversity of reared and natural populations of the black soldier fly, which is one of the most commercially important insects worldwide.
In their DNA
‘We carried out the most comprehensive black soldier fly sampling that we are aware of and used the findings to generate a comprehensive library of mitochondrial DNA sequences linked to geographic data,’ says Aino Juslén, project coordinator based at the University of Helsinki, Finland. ‘These results will be important to current and future programmes for the artificial rearing, selection and intensive production of the black soldier fly.’
The DNA sequences have been uploaded to the publicly accessible database GenBank.
Furthermore, the FLYHIGH team found ways to improve rearing protocols for certain fly species. Researchers examined how factors such as temperature, humidity and diet can impact on fly growth. As well as the black soldier fly, the project assessed rearing processes for other artificially reared species, including the housefly and the green bottle fly.
As a result, new larval feeding techniques have been developed and the performance of certain strains of fly species has been evaluated on different growth mediums. The enhanced artificial-rearing protocols for both the housefly and green bottle fly increased maggot activity and produced flies more effectively and sustainably.
Spotlight on species
Under laboratory conditions, FLYHIGH also studied the life cycle of flies with different positions in the food chain, such as hoverflies and blow flies, including their close relationships with certain plants. Both species groups could have applications in natural ecosystems or agricultural environments as plant pollinators or to help decompose organic waste.
‘We documented the specific requirements for each studied species group to survive in artificial-rearing conditions and eventually reproduce in captivity,’ explains Juslén.
The project collected data for fly species distributed in Mediterranean ecosystems of South Africa and Europe. New host plants were recorded for some species, such as specific bulb plants like lilies and aloe succulent plants. The findings revealed that the amount of ingested pollen for fly survival varied considerably among the studied species.
This project was funded through the EU’s Marie Skłodowska-Curie actions programme which supports training of researchers and staff exchanges. The project delivered an active schedule of knowledge transfer through academic visits, training courses, fieldwork and scientific seminars.