DDG has their own cralwer[1], so it would appear it also gets its own search results, even if may get some search results from other search engines.

[1]: https://duckduckgo.com/duckduckbot

> In fact, DuckDuckGo gets its results from over four hundred sources. These include hundreds of vertical sources delivering niche Instant Answers, DuckDuckBot (our crawler) and crowd-sourced sites (like Wikipedia, stored in our answer indexes). We also of course have more traditional links in the search results, which we source from Bing, Yahoo, and Yandex.

So DuckDuckBot is not used for any normal indexing. All actual search results are from Bing, Yahoo and Yandex.

So their bot is only for instant answers, and DDG is really just a metasearch engine? I'm a bit disappointed by that.

Might as well change to Searx then. It's also "just" a metasearch engine, but at least it's fully free/libre.

I wonder if there are any well-established free search engines that do their own crawling?

> Bing and Google each spend hundreds of millions of dollars a year crawling and indexing the deep Web. It costs so much that even big companies like Yahoo and Ask are giving up general crawling and indexing. Therefore, it seems silly to compete on crawling and, besides, we do not have the money to do so. Instead, we've focused on building a better search engine by concentrating on what we think are long-term value-adds -- having way more instant answers, way less spam, real privacy and a better overall search experience.