Unusual fly infestation

Hi guys, I would like help understanding the reason for a fly infestation in my area, these flies are uncommon, they appeared a few years ago, and now they’re everywhere. Rumors that they are flies created for biological control of other species.
In the image there is a sample of them, they like dead animals more, and thousands accumulate. Appear to be flies from the family Calliphoridae, but as I said, they are multiplying in an absurd way.
Obs: I would like to apologize, I do not speak English and this text has been translated.
The location of this infestation is -27.527964, -52.157723 (With reports within a radius of 40km) in Brazil.


Welcome to the forum @tobiasheitor !

I have never heard of flies being bio-engineered as control for anything. For me there are two likely scenarios for the reason behind the increase in these particular flies:

  • Certain environmental conditions have changed recently, which have become favourable for the flies - maybe an increase in food, a change in temperature and/or humidity, decreased populations of predators in the ecosystem (birds, spiders, etc).

  • The second scenario is that this is an invasive species recently introduced to the region and are multiplying quickly, due to the ecosystem not adapting to the new arrival yet.


I suspect the second scenario is what is happening here, because most calliphorids in the Americas are invasive.

1 Like

@zdanko @edanko @phycus Any idea of what fly species are those?

I would recommend posting this to the iNaturalist site for an ID.


These flies will not control pests. A few fly species, like botflies and mosquitos (male, so they cannot fertilize females), have been engineered to reduce dangerous (to humans) pest species. They tend to be ‘broadcast’ over specific areas by aircraft. Unless this is a large scale - greater than 40 sq. km - I don’t think this is a bio-engineered organism. Calliphorids seems like a good call. By the way, do not apologise for not speaking English - I routinely translate comments into French out of respect for Quebecois observers.

Essas moscas não controlarão pragas. Algumas espécies de moscas, como moscas-varejeiras e mosquitos (machos, portanto não podem fertilizar as fêmeas), foram projetadas para reduzir espécies de pragas perigosas (para humanos). Eles tendem a ser ‘transmitidos’ por aeronaves em áreas específicas. A menos que seja em grande escala - maior que 40 km2 - não acho que seja um organismo de bioengenharia. Calliphorids parece ser uma boa pedida. A propósito, não se desculpe por não falar inglês - eu costumo traduzir comentários para o francês por respeito aos observadores quebequenses.
I do not speak Portugese!


Chrysomya sp. Introduced from Africa/Asia.


Like Even said, these are Chrysomya spp., which weren’t introduced for a specific reason. There are some species like Cochliomyia homnivorax that have, for example; that species had sterilized males introduced in the Florida Keys to stem the existing population from continuing to grow, and therefore they all died out.


Yeah, they were very likely introduced accidentally.

1 Like

This topic was automatically closed 60 days after the last reply. New replies are no longer allowed.