[nkurz]

While technically true, I think that's in tropical Africa. Are there also diseases that they carry in North America? Even without disease, I tend to agree with the OP that black flies are worse than mosquitoes, and don't think I've ever heard of anyone getting a disease from a black fly bite in the US or Canada.

[capitainenemo]

You're mostly correct, but apparently not totally :) - I did think that it was further north, but the human cases are usually only in south and central america and africa. Nonetheless, there are some.

https://pmc.ncbi.nlm.nih.gov/articles/PMC4809994/ (human cases in the US - but is primarily in animals)

https://www.merckvetmanual.com/poultry/bloodborne-organisms-... (birds only, but still north american disease)

There's also an allergic reaction apparently due to large numbers of bites called simuliotoxicosis / black fly fever.

There's also this mysterious one in europe. https://pmc.ncbi.nlm.nih.gov/articles/PMC7920075/

Aaaand there's this site claiming possible encephalitis transmission, although I kinda feel I'd prefer a better cite than that. https://www.mosquitomagnet.com/resources/faq-black-fly-other...