bat
蝠 centers on the animal bat, specifically the small flying mammal.
蝠 combines 虫 (insect/creature) with 畐, which likely contributes the sound フク. The character was used to represent the bat, a creature that was sometimes classified with insects in older Chinese taxonomy.
The left side 虫 suggests a small creature, and the right side 畐 looks like a bat with spread wings and a body. Together, 蝠 is a bat.
For フク, imagine a bat flapping its wings with a soft fuku fuku sound as it flies through the night: fuku -> フク.
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bat (Chiroptera spp.)
fraternal myotis (Myotis frater); long-tailed whiskered bat
Indian flying fox (Pteropus giganteus); greater Indian fruit bat
Kitti's hog-nosed bat (Craseonycteris thonglongyai); bumblebee bat; Old World hog-nosed bat
Shinano whiskered bat (Myotis ikonnikovi hosonoi); Hosono's myotis
brown long-eared bat (Plecotus auritus); common long-eared bat; brown big-eared bat
Daito flying fox (Pteropus dasymallus daitoensis)
fruit bat (Pteropodidae spp.); flying fox; megabat
tube-nosed fruit bat (Nyctimeninae spp., esp. the common tube-nosed fruit bat, Nyctimene albiventer)
Hilgendorf's tube-nosed bat (Murina hilgendorfi)
Japanese house bat (Pipistrellus abramus)
Ussuri tube-nosed bat (Murina ussuriensis)
Japanese noctule (Nyctalus furvus)
Bonin flying fox (Pteropus pselaphon); Bonin fruit bat
Bonin flying fox (Pteropus pselaphon)
little Japanese horseshoe bat (Rhinolophus cornutus); Japanese lesser horseshoe bat
birdlike noctule (Nyctalus aviator)
Asian particolored bat (Vespertilio sinensis)
northern Ryukyu fruit bat (Pteropus dasymallus dasymallus)
Okinawa flying fox (Pteropus loochoensis)