The Bug Buffet: A Fly Angler’s Guide to Trout Food
If you want to catch more fish, you need to understand what’s on the menu. Trout are selective feeders, and their diet is driven by the insect life in their environment. Knowing how these bugs live, hatch, and behave helps you pick the right fly and fish it the right way.
In this guide, we’ll break down the three major insect groups—Mayflies, Caddisflies, and Stoneflies—and touch on some other key food sources like Midges, Scuds, and Sow Bugs. We’ll also highlight where to find these insects in Northern California and how they impact trout feeding behavior.
Mayflies: The Delicate Dancers of the River
Mayflies are the classic fly fishing insect. Their hatches are predictable, their emergence is dramatic, and their presence on the water often sends trout into a feeding frenzy.
Life Cycle: Mayflies go through four main stages—egg, nymph, emerger, and adult (which includes the dun and spinner phases).
How They Emerge: Mayfly nymphs spend most of their lives crawling along the river bottom, clinging to rocks, vegetation, or burrowing in soft sediment. When it’s time to hatch, they become more active, often drifting in the current before rising to the surface. Some mayfly species, like Pale Morning Duns (PMDs), emerge directly from the water’s surface, while others, like Green Drakes, crawl onto rocks or logs to hatch.
Emerger Stage: As nymphs reach the surface, they struggle to break through the water’s surface tension. This is a vulnerable moment—many get eaten before they ever become winged adults. Fishing an emerger pattern just below the surface can be deadly during a hatch.
Dun Stage: Once the mayfly escapes its nymphal shuck, it becomes a dun—a winged adult that sits on the water to dry its wings before flying away. Trout key in on duns sitting motionless on the surface.
Spinner Stage: After mating, mayflies return to the water to lay eggs and die. These spent adults, called spinners, lay flat on the surface, often in large numbers, making an easy meal for trout.
Food Availability: Mayfly nymphs are available year-round, but hatches bring peak feeding opportunities. Trout often switch from eating nymphs to surface flies when a hatch is heavy.
Where to Find Them:
Lower Sacramento River: Home to strong PMD and BWO (Blue-Winged Olive) hatches.
Hat Creek: Known for epic Green Drake hatches in late spring.
Upper Sacramento River: A reliable place to find BWOs during cooler months.
Caddisflies: The Workhorses of the Trout Stream
Caddisflies are some of the most widespread and reliable food sources for trout. Unlike mayflies, they don’t rely on the surface to hatch, making their emergence quicker and more explosive.
Life Cycle: Caddisflies go through four stages—egg, larva, pupa, and adult.
How They Emerge: Caddis hatches happen fast, often triggering aggressive surface takes from trout.
Larval Stage: Caddis larvae live on the river bottom, either free-living or inside protective cases made from sand, gravel, or plant material. They are available to trout year-round, especially when dislodged by currents.
Pupal Stage: When it’s time to emerge, the caddis pupae become highly active, swimming toward the surface or crawling onto nearby rocks. Unlike mayflies, they don’t need to struggle through the surface tension.
Adult Stage: Once free of their pupal cases, caddisflies quickly take flight, spending less time vulnerable on the water. However, when they return to lay eggs, they can skitter and bounce on the surface, triggering explosive strikes from trout.
Food Availability: Caddis larvae and pupae provide a steady food source. During hatches, the fast-moving pupae are irresistible to trout. The egg-laying adults also bring exciting dry fly action.
Where to Find Them:
Lower Sacramento River: Hydropsyche (tan caddis) hatches in the summer bring fish to the surface.
Feather River: October Caddis hatches in the fall offer some of the biggest caddis emergences of the year.
McCloud River: A mix of case-building and free-living caddis species make this a great river for caddis patterns year-round.
Stoneflies: The Big Meal Ticket
Stoneflies are the heavyweight food source in many trout streams. They require fast, well-oxygenated water, making them common in freestone rivers and mountain streams. Because they don’t hatch on the water’s surface, they are often overlooked—until you see a trout slam a big stonefly dry fly.
Life Cycle: Stoneflies have three main stages—egg, nymph, and adult.
How They Emerge: Unlike mayflies and caddisflies, stoneflies don’t emerge in open water. Instead, they crawl onto rocks, logs, or streamside vegetation to shed their exoskeletons and become winged adults.
Nymph Stage: Stonefly nymphs live on the river bottom for one to four years, making them a consistent food source for trout. They are poor swimmers, so when they get dislodged by strong currents, they tumble downstream—this is when trout take advantage.
Adult Stage: Once they hatch, stoneflies mate on land and return to the water to lay eggs, often skittering across the surface. This erratic movement triggers aggressive strikes from trout.
Food Availability: Stonefly nymphs are available year-round, but the adult emergence brings the most exciting fishing. The best dry fly action happens when large species like Salmonflies and Golden Stones return to the water.
Where to Find Them:
Upper Sacramento River: Golden Stoneflies hatch in late spring and early summer.
North Fork Feather River: A hotspot for Salmonflies in early summer.
McCloud and Pit Rivers: Home to a variety of stonefly species, making stonefly nymphs a go-to fly choice year-round.
Other Important Trout Foods
Midges: Tiny but essential, midges hatch year-round and are a primary food source in winter. The Lower Sacramento and Yuba Rivers are great places to fish midge patterns.
Scuds and Sow Bugs: More common in stillwaters and tailwaters, these crustaceans thrive in places like Baum Lake and certain sections of the Lower Sacramento.
Put This Knowledge to Work
Matching the hatch is one of the most rewarding parts of fly fishing. Understanding how these insects emerge—and when trout are most likely to eat them—will help you catch more fish.
Want to take your entomology game to the next level? Book a guided trip or join one of our fly fishing clinics. We’ll teach you how to identify hatches, pick the right flies, and fish them effectively.
Learn more and book your adventure. Every cast is an adventure—make yours count.