These had solar panels on them that loaded a capacitor and when it was full would discharge, causing the speaker to chirp.
Image by buschap
http://t.co/j3JjRL3b Set of 3 Solar Power Ladybird Bug Lights String Garden Lamps - by venditoruk (Venditor)
Cradling the solar bug zapper in my lap. It's not helping. - by iSolutionsASD (isolutionsforautism)
Forum: TEKKIT - Bug Reports • Re: LV Solar Array Lost: The HORROR a LV solar array.. Next you'll be reporting yo... http://t.co/aavyohNH - by MinecraftDK (MinecraftDK)