Pale morning duns are the big news on many Montana rivers this month. These ubiquitous little insects can create intense hatches that make trout feed aggressively on the surface--and make anglers' hearts thump loudly. It's not a difficult hatch if you have the right flies, such as size-18 Sparkle Duns, PMD Cripples, Parachute PMDs, or No Hackles. Hatches are usually in the morning and evening, but there will be only one hatch at midday if it's a cool, overcast day; if it's very hot, there may be no hatch at all. The quieter and clearer the water, the less hackle your fly should have. A downstream presentation is often needed on slow water or spring creeks. For some good tips on the PMD hatch, see Stages of the PMD Hatch. Expect evening spinner falls; a Rusty Spinner is a good choice for most streams. Hatches are strongest early in the month, and will start to fade in the second half of July.
Pale evening duns can be expected on many rivers this month. They are larger than the PMDs, but the same tactics and patterns (adjusted for size) are effective.
Yellow sallies may be either yellow stoneflies or yellow versions of little green stoneflies, depending on where you are. Trout don't have names for them--Latin or English--and if you match the size and color of the natural you'll do well. The afternoon and evening hours are the best times to fish an adult pattern. For flies and some tips, see Beyond the Big Stones.
Caddis are the other big news in July. Most of the action is in the afternoon and evening. Often, dry fly fishing just gets better and better as you get closer to dark. Many anglers go home too early and miss the best fishing of the day. The important thing to remember about caddis season is: "close is good enough." There are so many caddis species and so much variation in size and color, that you seldom need the perfect imitation like you sometimes do for mayflies. Choose a size and color and comes close to the prevailing insects. Next, choose a pattern based on the type of water: a well-hackled, high-floating fly for fast, rough water; a flush-floating fly with less (or no) hackle for slow water with a smooth surface. Above all, a good presentation is essential.
Hoppers will become important near the end of the month. Beetles and ants are important all month. For tips and flies, see Western Hatches: Terrestrials and Tying Better Ant Patterns.
Tricos are another hatch that takes center stage near the end of July. Some rivers have low flows at this time, which means warmer water temperatures and an accelerated hatch schedule. So be prepared for tricos by mid-July, just in case.
Some Montana rivers will have late or remnant hatches of golden stoneflies or even salmonflies this month. For tips and flies, see Fishing the Salmonfly Hatch.
Hot weather will push the fishing into the morning and evening hours. It can be difficult to get trout to come up during the afternoons, but you can still pick up some fish if you use your dry fly as an indicator and tie 24-30 inches of leader to the hook bend; attach a size 12-16 Copper John, Pheasant Tail, or Prince on the end of the dropper. Shorten the dropper length for evening fishing.
If the water temperature is 72 degrees or over, DON'T FISH; it's too hard on the trout.