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Research in the field of entomopathology has always aroused more interest in stinging insects, especially blood-sucking ones, which are carriers of severe and even fatal diseases. The mosquito would, for example, be the animal that caused the most human casualties in the world. The pathological involvement of other seemingly harmless insects is still very little understood, with a new study published in the journal Insects showing that the housefly could potentially pose a greater threat to humans (than the mosquito). By consuming exclusively liquid, this insect would vomit on food to pre-digest it, and could therefore carry dangerous pathogens.
There are over 80,000 different fly species worldwide, with morphology varying considerably from one species to another. Some may bite and feed on human or animal blood, ripping off (with their mandibles) a piece of flesh to gain access to the capillaries. Others feed only on torn flesh, decomposing it, or simply feed on decaying organic matter. Some also have a very specific diet, such as the cherry fly, which, as the name suggests, feeds exclusively on cherries.
Housefly: potentially more dangerous than mosquitoes
Lacking mandibles, “non-biting” flies feed exclusively on liquid. Landing on solid food, they first regurgitated a mixture of saliva and pre-digested food residues in order to pre-decompose them and suck them up, grabbing them drop by drop with their paws.
According to researchers at the University of Massachusetts, the housefly should be the most feared because, as an omnivore, it lands and feeds on anything that can provide it with nutrients and energy. Found in abundance in both rural and urban areas, it can be found on fresh or spoiled food, on the discharge of sick people, on stools, etc. It is particularly attracted to heat and certain odors such as sugar and decay.
Each time they eat, they regurgitate some of what they have previously eaten, including pathogens (contained in feces, for example). They fill a kind of pocket like a reservoir, which would serve mainly as a place of storage, and not digestion. This pocket serves as both a reservoir of enzymes, which they spit out to pre-decompose food, and a reservoir of food – which will then pass into another pocket for digestion.
Thus, the pathogenic agents they can ingest are not completely digested, and the storage pocket is provided with only a few enzymes. Namely, that they are covered in whatever decayed matter they land on (and then land on us or our food). Although blood-sucking flies and other biting insects that have direct access to the bloodstream are often considered more dangerous, “we have to be careful of those who live among us, as they get their nutrients from humans and animals that shed pathogens into their tears.” , faeces. and wounds,” warns John Stoffolano, professor of entomology at the University of Massachusetts and lead author of the study.
Because of this, the housefly can easily transmit diseases such as cholera, salmonellosis, typhoid fever, tuberculosis, etc. In addition, some flies that have developed resistance to insecticides may harbor antibiotic-resistant pathogens.
Important member of the ecosystem
However, it should be noted that, despite the generally negative attitude towards the fly, it is part of an important ecosystem service. Through the consumption of decaying organic matter, it plays an important role in the elimination of waste products, which subsequently feed on other insects or bring plant nutrients to the soil. The fly is also one of the pollinators and contributes to the reproductive cycle of plants.
On the other hand, it is also part of the food chain, which includes many species, such as birds, batrachias, arachnids, etc. The desire to eradicate it would thus upset the fundamental balance that has been established in the biosphere for millennia.