Like Emily, I also noted the meaning of the insects in Blue Velvet. Although everything in the town seems picturesque, beneath it all there is ugliness. The insects represent Frank and his cronies, who live in this perfect town yet bring evil to it. We must not forget, though, about Sandy's dream:
"I had a dream. In fact, it was on the night I met you. In the dream, there was our world, and the world was dark because there weren't any robins and the robins represented love. And for the longest time, there was this darkness. And all of a sudden, thousands of robins were set free and they flew down and brought this blinding light of love. And it seemed that love would make any difference, and it did. So, I guess it means that there is trouble until the robins come."
The robins represent Jeffrey. He is the light to the town, the person who is going to get rid of the evil insects. His posing as an exterminator is one way David Lynch helps the viewer see that. Jeffrey is a robin to Dorothy, because he is exterminating her pests, and he is a robin to Sandy because he represents love; remember that she tells Jeffrey she loves him while they are dancing. Jeffrey has made all the difference to Dorothy and Sandy.