Will insects enter the attic through ridge vents? Will insects enter the attic through the built-in end plug on ShingleVent II?

The vents have design features to help prevent this.

The code standard for the allowable space to prevent insects from entering vents has been set at 1/8? and applies to all gaps. The louver openings on the sides of ShingleVent II and the end-plug staggers are set at 1/8? and should prevent most insects from entering. This same reason is why screening used for rectangular undereave vents and the holes for continuous soffit vents (types of intake vents) have 1/8? holes in them. One bonus to the internal weather filter is that it also protects against insects that are small enough to get through the louvers from getting into the attic. The real-world bottom line however is this: if an insect is small enough to go through the louvers on the ridge vent, there are a lot of other openings in a house that the insect could enter through as well.