lizard
蜴 centers on a specific type of reptile: a lizard. It is not a general animal term but refers to the lizard creature itself.
蜴 combines 虫 (insect/reptile) with 易, which likely contributes the sound. The character is used specifically for lizards, a type of reptile.
The insect radical 虫 on the left hints at a small creature, and the right side 易 looks like a quick, darting shape. Picture a lizard scurrying away: 蜴 is a lizard.
For エキ, imagine a lizard basking on a rock, and when you try to catch it, it lets out a quick 'eki!' sound as it darts away. The 'eki' sound cues エキ.
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lizard
Komodo dragon (Varanus komodoensis)
don't judge a book by its cover
Gila monster (Heloderma suspectum)
Yemen monitor (Varanus yemenensis)
savanna monitor (Varanus exanthematicus, species of carnivorous monitor lizard native to sub-Saharan Africa); Bosc's monitor
Nile monitor (Varanus niloticus); water leguaan
Iberian worm lizard (Blanus cinereus); European worm lizard
lace monitor (Varanus varius, species of carnivorous monitor lizard found in eastern Australia); lace goanna
black-headed monitor (Varanus tristis); freckled monitor
tuatara (primitive lizardlike reptile endemic to New Zealand)
Ryukyu tree lizard (Japalura polygonata)
ridge-tailed monitor (Varanus acanthurus); spiny-tailed monitor
heloderm (any venomous lizard of genus Heloderma, incl. the gila monster and the beaded lizard)
Salamander (poem by Octavio Paz)
emerald tree monitor (Varanus prasinus); green tree monitor
worm lizard; amphisbaenian
horned lizard; horned toad
legless lizard (esp. Anguidae spp., incl. glass lizards and slow worms)
girdle-tailed lizard