Learn Russian: Муравьи везде ползают, чтобы найти еду. - Ants crawl around everywhere in order to find food.

The word везде (everywhere) shows that the ants are moving in many different directions to cover an area, rather than traveling in a single straight line toward one specific destination. For this scattered, multi-way movement, we need the multidirectional verb ползать instead of the unidirectional ползти.

Could we use the imperfective verb искать instead of the perfective найти here?

Yes, but it shifts the focus of the sentence. Using the perfective найти means they crawl around in order to successfully find food, focusing on the result. If you used the imperfective искать, it would mean they crawl around in order to look for food, focusing on the ongoing process. Both are grammatically correct, but найти emphasizes the final goal.

Why is the infinitive найти used after чтобы instead of a conjugated verb?

This happens because the subject doing the crawling (the ants) is the exact same subject doing the finding. When the subject of the main clause and the purpose clause are identical, чтобы must be followed by an infinitive.

The singular word for ant is муравей. Why does the plural look like муравьи instead of just dropping the -й for an -и?