"Crawling with" is a common phrase used to describe a high population density of insects, vermin, or other small organisms. However, there are many other words and phrases that can be used to convey the same meaning. For example, "infested with," "teeming with," "swarming with," or "overrun by" can all effectively convey the idea of a large number or overwhelming presence of pests or creatures. Other options include "crowded with," "packed with," or "overflowing with." Ultimately, the choice of synonym will depend on the context and the desired effect, but there are many alternatives to "crawling with" that will work equally well.