Caddis are hardy insects and have thrived in streams that have been decimated with pollution. Streams like the Tulpehocken, Oil Creek, and Casselman are just a few streams known for their abundant caddis fly populations in our region. For many of these streams, the caddisfly is so prolific that mayflies are an often afterthought for anglers.
The caddis behavior is a little less predictable and is certainly one of the reasons it is not as popular for many anglers. Many mayflies can be timed to within a few days and hours. The Green Drakes on Penn's Creek is revered by anglers the same way the "Swallows" of Capistrano are anticipated at the Mission San Juan Capistrano. Caddis not so much.
That is not to say great hatches of caddis are not enjoyed by anglers and trout, as there can be wonderful evenings and days with them covering a stream. Just as often there can be sporadic emergers happening without much fanfare.
There are over 1200 species of caddisflies in the country. They range in size and colors covering the gambit of black, green, tan, cream, and white bodies. The more popular Grannom hatch does arrive across much of the region at the end of April and is much anticipated by anglers and trout alike.
To get some understanding of their cycle it is as easy to do as by simply lifting a rock the next time out on the water.
As the caddisflies mature they reach the pupa stage where they hold up inside their cases and prepare to emerge out as adults above the water. This transformation from water to wing is the most dangerous for all insects. The caddisfly rises from their cases often with the help of a small gas bubble pulling them towards the surface. Once there they emerge with their uniquely folded tent-style of wings they take flight.
The caddis return to lay their eggs either on the surface or by diving to the bottom depending on the species. Like when they emerge, this is the time when they are most susceptible to hungry trout. The cycle of life then returns as these eggs transform into the larvae again.
Like mayflies, caddisflies begin in earnest in April and are a big part of many streams. Continued sporadic hatches can be found through the late Fall.
To learn and discuss more mayflies on the site head over to the Hatch and Entomology Forum. Beginners can follow along and learn more in the Beginners Forum.
A great online site to follow and get deep into the Latin is Troutnut and his Aquatic Insects of our Trout Streams. A must-read!!
For further reading check out Gary LaFontaine's book Caddisflies.