Their aforementioned nasty passive, Dissolve, will also fully restore a GlowFly's mana, with which they'll use a similar mechanic to the MushroomCore boss. They can Replicate using 10 mana and half their HP to create a token copy of themselves with 0 mana. Combined with the above passive and Regenerate, you'll be swarmed by semi immortal bugs if you can't take them out fast enough. Large scale attacks like MeteorStorm or Tsunami are advised. Having a Radiation immune team will slow down their growth in numbers, since Dissolve only restores their mana if they can successfully inflict Radiation.
They can be sold for 100 gold at Medium size and for 300 gold at Enormous size. Every level above 1 additionally increases their price by 5%.