The GTi Caddis is more imitative than most of my patterns.  It represents a hydropsychidae larvae, commonly called "net builder" Caddis.  Though a bit cheesy, GTi stands for Go-To imitation.  This pattern truly is my go-to when wanting a weighted fly that closely imitates a favored large food form of Trout.  One thing you'll notice when comparing real Hydropsyche to my imitation is that the back on the GTi does not necessarily match any of the color combinations of the real insect.  This isn't by chance.  I've spent a fair bit of time tying and trying Caddis larva imitations and I've come to learn a bit about what fish prefer in the process.  For reasons unknown to me, Trout consistently prefer this fly when tied with a shell back color that contrasts the under body.  I've tried many imitations that more closely represent the actual colors of Caddis larvae, but the fish do not take them as well.  There is something magical about the contrasting colors.  Try it, you'll like it... Get a few GTi’s and fish them in your favorite Trout water.