Preferred damselfly nymph habitat includes dense mats of submerged vegetation, such as chara, coontail, milfoil and pondweed. Damselflies can spend up to four years in the nymphal stage before making the transition to an adult. The nymphs undergo multiple molts or instar stages as they grow from minute creatures to 1.5-inch long mature nymphs. Lush vegetation that covers the shoal, or shallow zones, of a lake provide an abundant hunting ground for these carnivorous insects. Nymphs feed on scuds, mayfly nymphs, zooplankton and any other meaty food sources they can capture in their extendable mouthparts. These are not fast swimming predators, but stalk and ambush specialists. Nymphs are adept at matching their body coloration to the habitat they live in, so it is not uncommon to have multiple colors of the same species of damselfly in the same waterbody. Damselflies undergo an incomplete metamorphosis, which means there is no pupal stage such as found in midges and caddis. The fully developed damselfly nymph leaves the protection of its benthic habitat and swims to patches of emergent vegetation, like longstem bulrush, cattails or sedge grasses. The nymphs swim in a sinusoidal motion using their three-lobed caudal lamellae or “tails” to propel them through the water. Once reaching the plant stalks the nymphs crawl out of the water. Their exoskeleton dries and splits open allowing the adult to crawl out. Newly emerged adult bodies are soft and delicate and it takes up to several hours for their bodies and wings to harden. They then fly off and spend the rest of the open water season eating adult mosquitoes, midges and other small flying insects. Adults mate and females deposit eggs in emergent and floating vegetation. Females also crawl down emergent plant stalks and deposit eggs well below the surface. Adults live well into the fall season, but die off along with their prey with the arrival of freezing air temperatures.
It’s the nymphal stage that really attracts the attention of trout. One of the most intense and frenzied feeding periods occurs during the mature nymphal migration. Typical emergence occurs during the early summer season while water temperatures are still increasing, but prior to the onset of hot summer air temperatures. Overall, the hatch is short, often less than a couple of weeks in duration. Fully developed nymphs, in large numbers, swim from the lake bottom to within a few feet of the surface, then travel horizontally en route to concentrations of bulrush and cattail. During this migration the nymphs are fully exposed to trout cruising the shoals and edges of drop-offs. Fish pick off nymphs at will while never showing any signs of surface activity. Anglers see the swimming nymphs in the water or hanging from the stems of emergent plants. Pulling anchors at this time of the year often results in several nymphs falling into your boat or onto your float-tube. Things get even more interesting when masses of nymphs, emerging nymphs and newly emerged adults cling to the stems of rushes and sedge grasses. A gust of wind pushes the helpless insects into the water making for a very easy meal for trout willing to feed in water often less than four feet deep. At other times aggressive trout roll into bulrush stems to send the food purposely crashing onto the water. This is an amazing sight that leaves an angler shaking as they scramble to tie on an adult pattern. Fishing patterns tight to or into the bulrush or cattails is exciting and a real challenge when the trout decides to run even further into the forest!