At first Clark's waiting to tell Lois about the bugs made sense, since he did not want whoever set them up to know he had figured it out. However, I realized when he was explaining them that there was no way for him to give Lois a good explanation of why Superman did not get rid of them that morning without her knowing he was Superman.
I still have to agree with Lois that the reasoning for waiting to tell her does not add up. In fact, thinking through it again I do not see why Superman did not tell her. It was not like anyone would find it odd that Superman flew by to see that Lois was OK, and while Perry did give him a "get down to Henderson now!" order, a short stop by Superman to at least warn Lois would not have really taken extra time. Although maybe I am underestimating the difficulty of a short stop by Superman by Lois' place.
