Because of the huge diversity of this order of insects (Trichoptera) the simplest form of identification is to group the insects by larval behavior. The following keys are broken down into 3 types of larval behavior, case builders, net spinners, and free living caddis. This key is more of an introduction to caddis rather than a functional key, with over 12,000 species it would be an impossible task to identify each and every one. Simple put, there are more caddis species than stonefly and mayfly species combined. Even at the Genera level there is 143. There is hope however, as a fly fisherman it is important to identify the insect and its basic characteristics. The following keys should help you do just that.
The Caddis fly has over 12,000 species in North America, more than all the mayfly and stonefly species combined. Even with all this diversity, they still take second place to mayflies in the east and stoneflies in the west. Their obscurity may be a direct result of their diversity; it is very difficult to catalog categories and imitate all of the caddis fly species. That all said, caddis flies are a very important food source for trout, and of equal importance to the fly fisher.
Caddis flies go through full metamorphosis, giving the fly fisherman three stages of life to imitate. The larval stage can be broken down by behavioral characteristics. Three basic behavioral characteristics are case building, net spinning and free living. The case building caddis use a myriad of material, both organic vegetation and rock or sand, to make their homes. Perhaps you have seen a small bunch of sticks or pebbles walk across the stream bottom. The free-living larva are voracious predators that feed on other small insects. Free living caddis live in riffles and fast currents, and because of their roaming life style, are available to trout year round. The net spinning caddis larva build stationary homes with catch nets. These nets are situated on the top of rocks in the main current to catch pieces of floating vegetation, and small organic debris, which the larva feed on.
The Pupa stage of the caddis fly is rarely seen by the fly fisherman, because of its fast transition to the adult stage. The pupa are fully encased inside a sealed cocoon on the stream bottom until they are ready to emerge. At the time of emergence, they break open the cocoon and swim very quickly to the water’s surface, where they explode into the air as a full formed adult. This rapid transition can cause trout to go wild. Trout may be seen leaping from the water as they chase the caddis flies from the stream bottom into the air.
The adult caddis flies mate soon after emergence in trees and bushes along the stream. They return to the water to deposit their eggs, usually at dusk. Caddis can lay their eggs in two different ways; one is called ovipositing, where the female flies over the water’s surface, releasing her eggs. Caddis may also dive under water or crawl down plants and rocks, depositing their eggs on the stream bottom. If you notice caddis on your waders while you are fishing some night, the green stuff on your boots the next morning will be caddis eggs.
Caddis fly larva have the following characteristics
- Six jointed legs
- Grub or maggot like appearence
- No tails
- Anal hooks
- May build a house with sticks, pebbles, leaves or other bottom debris
Caddis fly pupa have the following characteristics
- Long antennae, longer than their bodies
- Legs that dangle freely
- Short wing buds
Caddis fly adults have the following characteristics
- Tent shaped wings that fold over their back
- Wings will have small hairs all over them
- Long antennae