From Jeremy S Cook on the Tindie blog:

Jar O’ Fireflies Kit or Assembly

Relaxing outside on a hot summer evening you might catch a glimpse of fireflies as they perform an ethereal bioluminescent dance. Maybe you even been able to catch a few, trapping them in a jar for your entertainment. Recreate a bit of that magic with a DIY electronics project.

This FireFly Jar Kit presents a different, and much longer-lasting, bottle of blinkies. Instead of actual fireflies blinking, is emulates the bugs’ effect with tiny 0603 LEDs and 38 AWG wire. An ATtiny85V provides lighting control, and it should be able to function on its CR123A battery for 6 months or more.

While you can build this type of contraption yourself, the item listed here is available fully-assembled, as a kit, or a PCB only. In either case, you don’t have to mess about with making your own PCB or perf board assembly, which could be well worth the $30, $20, or $10 price tag. Personally, I much prefer to avoid soldering as much as possible, especially if the terms “0603” and “38 AWG” are involved. Soldering concerns aside, be sure to check out the representative video of this type of faux firefly effect below: