This is the second version of the  Chernobyl Ant that I have found.  I have not tried this one but will this summer.  From all reports this version is also very successful at bringing trout to the surface,

Material:

1.  First off wrap a nice even base of thread starting from near the front of the hook and extending to the point where you are going to tie in your first part of the fly, the tail. This point should be roughly level with the barb on the hook. Also cut two sections of foam as shown and then move to step 2.

2.  Place these two pieces of foam on top of each other, black over beige and tie in about 3/4 down hook shank. Wrap a number of turns of thread in the same plane until the foam is securely anchored in place. If using 6/0 you will find it difficult to get the foam as secure as desired and we would recommend using at least the 3/0 preferably A+.

3.  Take a section of rubber legs from your occy strap or from the packet if you have bought them from a fly shop. Tie in on the side of body so that the legs flare out. It might take some fiddling initially to get it right but after a few goes you should be able achieve this with very little effort. Once you have done this add a second set of legs on the opposite side of the body.

5.  Now we are back in the horizontal plane. Now add some of the dubbing to the thread and wrap a small ball of dubbing in front of foam. This is not a must do it's just something that we have been shown and have used on our CA patterns ever since. 

6. Pull the foam body over the top of the dubbed body with your right hand while pinching a small hump in the foam with the thumb and forefingers of your left hand (for right handed tier). You are then right to tie in using several tight wraps in the same plane as in Step 2.

7. We can now start adding the second set of legs. Take a piece of your rubber leg material and tie at the front (about 1/3 from eye of hook)and again on the side. Don't worry if it is too long at the moment as we will be trimming them later on. Notice the clearly defined segmentation of the body that we have now.

8.  Add a second set of legs just as in earlier steps. The fly could be pulled straight from the vice and fished as is but we will do a few little things to finish off. Add a few more wraps in the same plane for strength as we want this fly to be pretty much indestructible

9.  Again notice the segmented look of the fly and the oversized rubber legs that give the fly an amazingly lifelike appearance when on the water. Next step is to add a small sighting indicator as this can be a tough pattern to see in rough water.

10. Cut a small piece of Yellow closed cell foam. Tie in just above dubbing and in the spot where you have just tied in your front set of legs. You only need a few wraps to anchor this securely to the fly and once again you don't have to add this to the fly. I tie some with/without although it must be said you can always trim it off later if need be. Whip finish in the same plane.

11.The last step involves trimming the wings to shape. Use your own discretion here and don't worry too much about getting them exactly right. These insects sits on the surface with their wings all fouled up and it is more the presentation and reasonably accurate size, shape, profile that is most important.

12. Grab the tips of all the legs and pull it upwards away from the fly body. Trim them roughly evenly making them a little longer than the hook shank (we want that wiggle). The legs will fall down and settle in the X position.