fly
蠅 refers specifically to a fly, the common insect.
蠅 combines 虫 (insect) with 黽, which likely contributes a phonetic element. The exact historical development of 黽 in this character is uncertain.
The insect radical 虫 on the left paired with the complex right side 黽 suggests a specific kind of insect: a fly.
For ヨウ, imagine a fly buzzing with a high-pitched 'yo-' sound: yo -> ヨウ, as it circles around.
fly (any insect of infraorder Muscomorpha)
fruit fly (any insect of family Drosophilidae); vinegar fly; pomace fly; banana fly
gall midge (any insect of family Cecidomyiidae)
tsetse fly
flies swarming at the beginning of summer
take care of yourself before you take care of others; wave off your own flies before you wave off someone else's flies
housefly (Musca domestica); house fly
tachina fly (any fly of family Tachinidae); tachinid
ox warble fly (Hypoderma bovis)
melon fly (Bactrocera cucurbitae)
lauxaniid fly (any fly of family Lauxaniidae)
flesh fly (any fly of family Sarcophagidae)
louse fly (any fly of family Hippoboscidae)
Oriental fruit fly (Bactrocera dorsalis)
Lord of the Flies (1954 novel by William Golding)
Venus flytrap
small characters; tiny handwriting; as small as the head of a fly
greenbottle fly (esp. species Lucilia caesar)
bluebottle fly
completely helpless; unable even to drive away the flies on one's own head