@Vanessa1824. We have the same problem. Being in the countryside with lots of trees etc. We did have a guest leave at 1am in the morning because they woke up and saw a spider.
Because of this, I have noted it in the listing under the heading "Things to Know". Below is what I have written and hopefully guests read this and know what could be possible.
"Being in the middle of the countryside and trees, the area is tranquil and full of wildlife. This does include various types of insects, which at certain times of the year try to venture inside. Although every effort is taken to prevent insects inside the property, we obviously can't guarantee you won't get a visit from the odd woodlouse or spider"