I've never known any other word but hyttynen for the pesky, biting, blood-sucking, disease carrying insect (i.e., mosquito) which is as much a part of the Finnish summer as mansikka, kesämökki, and keskiyön aurinko. The other day, however, I came across itikka and found the following translations:
Wiktionary - mosquito (colloquial) hyttynen, moskiitto and sääski are listed as synonyms
Google Translate - bug
Glosbe - mosquito
EUdict - insect
Urbaani Sanakirja - Hyttynen, tai muu vastaava ärsyttävä pureva hyönteinen
LinguaTutor XL1000 (an electronic pocket dictionary made in Finland by Finns for Finns learning English) - hyttynen
My wife, who is Finnish, was skeptical about the itikka -> mosquitio translation as she's never heard it used to refer to a mosquito. Her parents, also Finnish, agree and further clarify

Is it a colloquial usage thing? Dialectal?
To which insects do itikka, sääsksi, hyttynen, and mäkärä/mäkäräinen refer?