Rivers: the large dark olives will start to tail off, while other upwing flies such as mayflies (above), medium olives and yellow mays will increase in numbers. Mayflies will hatch right through June though numbers peak at different times on different waters. Stoneflies will be hatching alongside alders and some sedges too. As far as terrestrials go, expect to see beetles and black gnats featuring high on the menu.
Stillwaters: Pond and lake olives should start to hatch in increasing numbers. Caddis flies will most likely be on the water too. On warmer days there will be big hatches of damsel flies (above) and their nymph patterns will work well around the margins and in particular near read beds where they often crawl out to hatch. There will be mayfly hatches through the month if the species is found there. Lots of beetles will be getting blown onto the water so tie up some foam ones.
