Sorry for the double post but I wanted to make sure Blanchflower saw this.
The new game code as long as you patched up is that Butterflies disappear at night now. In places where butterflies spawn, you can find fireflies. I started a new game in AP without placing any spawners and I found fourteen fireflies over the course of two nights. A collection helper would probably go a long way to helping you find them but like I said they are only available at night.
Edit: I reached 100% for my firefly collection with 8 fireflies but it doesn't show as complete in my Collection Skill Journal. Here is a picture of all 8 and their names plus quality. I put them by monetary value but I don't know the ranges. Fireflies do take over all butterfly spawns about 8 pm at night and disappear between 4 and 6 am. Butterflies start to appear again around 7 or 8 AM and disappear around 6 PM.
White - Firefly albus - common
Yellow - Firefly fulvus - common
Green - Firefly pratinus - common
Orange - Firefly luteus - common
Blue - Firefly caeruleus - uncommon
Red - Firefly ruber - uncommon
Pink - Firefly roseus - rare
Purple - Firefly purpureus - rare