Most are made with mesh covers so that your child can see out, and you can see in, but bugs will not be able to get to them. (babycarrierreviewguide.com)
You can also purchase a UV protective mesh cover which doubles up as an insect net, so they're good for indoor or outdoor use. (homemade-baby-food-recipes.com)
What I also like about it is that it has a zipper mesh covering that prevents your belongings from falling out while you are going over the rough terrain. (momsstrollerreviews.com)