Translation:Look, there are a lot of butterflies on these flowers.
Well, grammar says because the noun is singular you need the verb conjugated for the singular i.e. "there is a lot of them", and sometimes this is what is said. However in conversation a lot of people might say "there ARE a lot of them" which is grammatically incorrect. However most/more people would probably say "there's a lot of them", which is probably a good result. It sounds OK and is actually grammatically correct!