I actually find this sentence a bit gross/disturbing
"They" are probably bats. But I for one welcome anyone who wants to reduce the mosquito population.
Why cannot I use the word "pentru" here for the word "for"?
That's a good question. The answer is, in Romanian "ei mănâncă (something) pentru cină" sounds really weird. As if you'd say "they eat (something) into dinner". In other words, nobody would use pentru in this sentence.
Tantari si paianjeni la cina? Scarbos. Imi este foarte greu sa continui acest curs...