Helgramites are tiny centipede like water-insects. You can find them in many rivers and streams beneath rocks. Most people have never used them as no one seems to talk about them, I guess that’s because the people who do know about it want to keep helgramites a secret. Anytime in July, go for river smallmouths with them, I’ve had days where it seems like every cast I’m catching a lunker with them. Some companies also make artificial helgramites and they work pretty well too, although not as good as live.
Here’s a typical helgramite, try them, and good luck!