虫 on the left is the signific/radical (category), the other part is a phonetic element (pronunciation hint).
A traditional Chinese dictionary is arranged according to 214 radicals (部首 bùshǒu / buhshoou “category heads”), most of which are also meaningful significs (meaning hints). You only need to remember a few dozen of the most common ones, such as 虫:
“insect”
An observant person will note that centipedes (Latin cent “hundred” + ped, “foot”) and spiders are not insects. Centipedes and spiders are arthropods (Greek arthro “joint” + pod “foot”), animals with jointed legs. Arthropods are a much larger group which includes spiders, insects and crustaceans (animals with "crusts", such as crabs and shrimp).
The 2000-year-old Chinese 虫 signific (radical) includes such varied creatures as 螃蟹、蜥蜴、蛇 pángxiè, xīyì, shé / parngshieh, shiyih, sher “crabs, lizards and snakes”. This group of characters could be loosely translated as “critters” or "creepy-crawlies" ;-)
An earlier post that focused on 螳螂 tángláng / tarnglang the praying mantis (with an explanation of Chinese character structure and an idiom):
Who I Am
My nickname is an elegant phrase 文通四海 Wentong-Syhhae (four-character expressions are very popular in sophisticated Chinese) that means “Reach the Four Seas [by means of] writing”, an allusion to the fact that I have been a multilingual language teacher for almost all of my adult life.
Born in Paris, I spent my early years in Europe (details: https://steemit.com/introduceyourself/@wentong-syhhae/enthusiastic-intp-polyglot), and by the age of 20, I was fluent in five languages, so this nickname feels very appropriate. I spell my nickname according to GR rules, a tonal spelling system for romanizing Chinese.