I was lvl 50 something When I died near volcano with my ptera while tamming an argy and spawned back at my base I used my high lvl triceratops (247 something) to go back to volcano that's when I encountered this beasts it killed me and my trike very brutally and after that I had to start again I lost all my stuff at volcano it despawned and then later when I leveled up high enough to unlock spino saddle I tamed an spino of lvl 80 and took my revenge by killing 6-7 of this mosquitoes (not all at same time) I would not recommend going near swamps until you are high leveled or have a powerful and speed dino which can easily take on them I used spino for them you can use spino or any other high ranged and high dmg dino with good enough hp or you easily get killed

GOOD LUCK FIGHTING THIS MOSQUITOES...