It's an amazing thing - something in the back of ancient brain tells us to avoid bugs; to jump, scream and squish any that come near. Of course there is a good arguement for learned behaviour. A kid who is left alone will most likely pick up a carpenter (sow bug) and examine it. An opposite response would likely stem from observing others.
So, are you scared of bugs - is it a phobia? You may recall a movie called Arachnophobia? It highlighted one of the primary bug phobias - the fear of spiders (the phobia includes insects like scorpions). Most people do not like spiders and other insects. Choosing not to brush up against a spider's web or allowing some insect to scurry by at a safe distance is a normal, socially-driven discomfort with bugs.
This is a heavy topic. Most bugs weigh less than your fingernail and most will not cause harm. By the way, none of the hundreds of Newfoundland-based spiders which have walked across my hands have ever bitten me.