Insects (or bugs as we generally call them) are of course necessary in the natural environment. But they are everywhere! They get into our homes. They take part in our outdoor parties.
The first one is really simple. If I say "You are bugging me!" to someone, it means the person makes me angry, like a bug! Bugs can be pests (害虫), too. So, when someone really, really makes us mad, we could say "Stop bugging me!"
Ants can also be pests. They are so small that they can get everywhere. In fact, if we sit too long on the ground, they may even get in our pants. So, the expression "to have ants in your pants" means you cannot sit still. You are always moving around.
In places where the weather is getting warmer, insects like flies may be coming out to trouble you.
So, we can say "a fly in the ointment (软膏)" to point to something bad that makes something else worse.
Here is an expression used in a couple of sentences. Lucy's surprise party for her husband's birthday was nearly ready. The cake was made. And all his friends were hiding in their house. Then came "the fly in the ointment". His flight was called off, meaning he would miss his party.
And we really do not think twice about killing them. So, if someone is very kind with no violent (暴力的) feelings at all, we could say that person would not harm a fly.
A. The food was ordered.
B. Now, flies are everywhere.
C. So we have expressions that use insects or bugs.
D. Sometimes their appearance means that something bad is nearby.
E. If you get ants in your pants, you may move around to get them out.
