During the spring the best, and usually only, bet is to "match the hatch". After the Green Drake hatch in early June has signalled the end of the classic hatches, the lack of reliable hatches causes many anglers to give up in frustration and move on to other pursuits. This is just as well, for the observant fly rodder can still take fish on vastly less crowded streams. Fish are still eating every day, and, while it's true that they are concentrating on nymphs along the stream bottom, they often look up and take insects from the surface. The most prevalent "hatches" on the water's surface at this time are the land-bred groups of insects, or terrestrials.
Terrestrials inhabit the trees and grasses bordering the stream. Most of these insects reach maturity during late spring, and trout begin to feed consistantly on terrestrials as the aquatic hatches begin to taper off. Large numbers of these ants, beetles, grasshoppers, crickets, wasps, etc. fall or get blown into the water and become a significant part of the trout's diet. One of first mass-printed books in the English language, "The Compleat Angler", by Issac Walton, contains several terrestrial patterns; they've taken fish from the beginning of the sport.
Land-bred insects come in all sizes and are imitated in fly patterns from the big #2 and #4 Michigan Hoppers and Muddler Minnows to the diminutive #24 and #28 Jassids. It isn't necessary to carry such a large range of sizes; most of the time patterns from #8 to #20 will serve you very nicely. Even this range of sizes calls for tackle in "all-around" category. A 7' to 8' medium trout rod that balances with a double-taper, floating, #5 or #6 fly line and a lightweight single-action fly reel will handle most situations.
Terrestrials tend to hit the water's surface at random. Sudden gusts of wind or navigational errors deposit insects in all shapes, sizes, and colors throughout the day. Trout don't normally see "herds" of the same insect, so they don't become imprinted to a single type. The larger varieties represent a lot of protein in one tidy package, and trout will often move up to fifteen feet to strike the hapless victim. More often, however, a trout will pick out a lane in the stream's conveyer belt and causually sip terrestrials for hours at a time.
Next time you're afield, take note of streamside terrain, weather conditions, wind, and time of day. Grassy banks mean that hoppers, crickets, and aphids will be present; select a Letort Hopper or Cricket and cast it toward the bank of a slow, deep run. If it lands a little roughly, don't worry, since these insects rarely hit the water gracefully. Let the fly ride in the suface film a few feet, then take up enough slack in the line so you can impart a gentle twitch to the fly. Be ready for the fly to simply disappear from the surface. If nothing happens, let the fly ride with the current until drag sets in, then lift and cast again. After several tries, if you still don't have a fish, move quietly upstream to the next promising spot. You can search long stretches of water this way. Sooner or later, if there's fish around, one will show himself. If it doesn't hit your fly, switch to a smaller pattern in a different color until you connect.
Crickets are most active from early evening to mid-morning; hoppers are most active during the middle part of the day. Strong, gusty winds can put either insect on the water at any time of day. Letort Hoppers and Crickets are usually tied in sizes from #10 to #16. Use the Michigan Hopper or floating Muddler Minnow for the larger, shaggier varieties. These patterns use hollow deer hair for bodies, as do the inchworm, beetle, bee, and wasp. They float very well and work in slow or fast water.
My favorites are the various ant patterns. I've had more success with the black ant, but the red ant (actually a cinnamon brown) is an important pattern. Ants are plentiful along most streams, and trout really go for these creatures. The ant (and the pattern) float right in the surface film for a short distance and then slowly sink below the surface. A dab of flotant is necessary to keep the fly up.
Find a slow run and gently deposit the ant in the middle of it. Often you can't see the fly, just the dimple in the surface where it sits. Trout will sip on ants with all the nonchalance of a yuppie with a martini at a cocktail party. Slowly the trout rises, sips, and settles back into his spot to wait for another. If you can find some trout in the mood for ants, you're in for some fabulous fishing. Half a dozen ant patterns will cover your needs-- black and brown floating ants in sizes #10 to #20; #16 to #20 floating winged ants in both colors; and, sinking hard-bodied ants in two colors, size #10 to #16.
Two of the oldest patterns in the flybook, bees and wasps, will take fish due to their size; I rarely see them on the water, probably because they are very poor swimmers and sink quickly below the surface. Used as a wet fly with a floating line and a short fine leader should produce results. I've had much better luck using a bumblebee pattern called the "McGinty" as a traditional wet fly. Cast down and across the stream and swing the fly in the current until it's straight downstream from you. Most hits come on the swing.
Inchworms are seasonally and regionally important and some of my trouting buddies swear by them---I don't know because I've never caught a fish on one. Inchworm bodies are made of dyed green deer body hair in sizes #12 to #16. The strands are tied to the top of the hook and extend well past the bend of the hook. Lacquer the deer hair to seal the ends, and this fly will float forever. My experience notwithstanding, try these little guys---they do take fish.
Beetles abound along streams in summer. There are so many varieties that it's not necessary to make exact imitations. Fly tiers make patterns from deer hair for high floaters or lacquered feathers tied to the top of the hook for the in-the-surface styles. Deer hair types are bigger (#10 to #16) and more durable. The feather beetles are very delicate, but they produce some very big fish on #14 to #20 hooks. Take your choice of drab colors. (The wild metallic colors on beetles are mostly on their backs, not easily seen by the fish.)
The smallest terrestrials are the Jassids; they are usually tied in sizes from #16 to #28. These flies are most common along the grassy banks of slow moving limestone streams (i.e., south central Pennsylvania). They demand the long cast, fine leader fishing most commonly associated with summer fishing. Trout can become very selective about these insects calling for exact imitations fished with an expert hand. If you can get near the water without spooking fish, take a nymph net to catch some samples in the surface. Tie on your nearest imitation, stay out of sight of the fish, and unload your longest cast to a feeding fish. Good luck, you'll need it.
If you don't tie your own flies, start with terrestrials. They're easy to tie, most of the patterns are very durable, and best of all, they catch fish. Tie up a few and add the three months of summer to your trout season.