The vast majority of the flies you tie with have material wound onto the shank of the hook to form the abdomen/thorax of the fly. On smaller flies, I have experimenting with a more minimalist style of tying. On some patterns, I have simply used the tying thread for the abdomen with maybe a ribbing of thread as well. The results have been favorable for emergers & dries.
In the above pattern, the Olive Zelon tail/shuck was tied in at the thorax and the olive 14/0 thread was wrapped down the shank toward the bend and then back up to the thorax are. That is the extent of the body (abdomen). There is one turn of dyed olive peacock herl to form a thorax, a tuft of CDC for the swept back wing and a few turns of brown hackle. The thread head is finished off with the same olive tying thread.