Sounds like someone in his family has a fear of bugs and has passed it on. My teenaged son is terribly afraid of spiders and always has been...it has been so hard to get him not to pass that on to his younger siblings! Maybe you could get some bug catching boxes and books about bugs and plsatic bugs and make a theme of it? Maybe if he learned not to be afraid of the plastic bugs, he will be better with real ones? I don't know...I never managed to get my son out of it...so not sure how helpful I can be!