What type of chakra element does the Aburame clan possess? Among the five basic elements of chakra (earth, water, wind, lightning and fire), what type of chakra does the Aburame clan possess to control insects at their will?
I don't think it matters. The insects live under their skins in symbiosis with their host. The shinobi and the insects both benefit from this: the insects feed on their host's chakra (and I don't think they care about its type), and the host can use ninjutsu involving the insects. 

Note that ninjutsu must not necessarily be bound to a specific element. For example, Shadow Clone Technique is a ninjutsu which can be used by a lot of shinobi with different chakra types. Therefore, I think that Aburame clan members can have any chakra type.