Etymology corner (which may help some remember some vocabulary): there's a direct English equivalent of 'maur', which is 'mire'. It also means 'ant'. There's also 'pismire', which also means 'ant', but refers to the smell of formic acid you get when you kill one. Both words are a little archaic in most English dialects, mind.
Well, it's not really needed. 'An' is used before a word that starts with a vowel because it would be easier to hear and differentiate between the article and noun; compare "a elephant" and "an elephant". The first sort of merges 'a' and the 'e' in 'elephant'. Additionally, it's kinda unpleasant to say. Thus, the latter is much better in that situation. In Norwegian, 'en' already ends with a consonant so it isn't necessary to have another article before words that starts with a vowel.