noun
workaholic; person devoted to work
Describes someone who lives for work, often to the exclusion of other interests. The 虫 (bug) metaphor implies an obsessive, ingrained trait.
彼は仕事の虫で、休日もオフィスにいる。
He's a workaholic; he's at the office even on his days off.
ワーカホリック is a direct loanword for 'workaholic' and sounds more clinical or modern; 仕事の虫 is a more traditional, metaphorical expression.
Compound of 仕事 (work) + の (possessive particle) + 虫 (bug/insect). The 虫 metaphor is used for someone with an obsessive or ingrained trait, similar to 本の虫 (bookworm).