The noun 虫 (chóng) means 'insect,' 'bug,' or 'worm.' It is a general term for small crawling or flying creatures. It often appears as a component in compound words for specific insects, such as 毛虫 (caterpillar), 甲虫 (beetle), and 害虫 (pest).
窗户上有一只小虫在爬。
Chuānghù shàng yǒu yī zhī xiǎo chóng zài pá.
There's a little bug crawling on the window.
夏天一到,各种虫都出来了。
Xiàtiān yī dào, gè zhǒng chóng dōu chūlái le.
As soon as summer comes, all kinds of bugs come out.
他从小就怕虫,连蚂蚁都不敢碰。
Tā cóngxiǎo jiù pà chóng, lián mǎyǐ dōu bù gǎn pèng.
He's been afraid of bugs since he was little — he doesn't even dare touch ants.