Step 15: Use the rightmost angled line under the ant's thorax as a guide to draw the front leg. Draw the thin shape of the leg around the guide. Divide the long part of the guide into two segments. Divide the bottom part into small segments too and add a couple of spikes at the tip. Now follow the guide after the line bends and add the next segment. Make this one a bit thicker. On the left side, draw the segment that attaches to the thorax. Part of it will be hidden behind the previous segment.
Step 16: Use the angled line in the middle as a guide to draw the center leg the same way. Draw the long part of the leg first around the guide line. Divide the leg into two thin segments. Divide the lower part into small segments too and add a couple of tiny spikes at the tip. Now draw the rest of the ant's leg using what remains of the guide line. Follow the path of the guide to connect the leg to the thorax. Make these segments thicker than the lower segments.
Step 17: Use the leftmost angled line as a guide to draw the ant's hind leg. As before, divide the long side of the guide line into almost equal halves and draw the two segments around it. These segments must be pretty thin. You're basically just thickening up the guides. Add the spiky bits at the tip. Draw the thicker segment of the leg using the right side of the guide line. Draw a couple of lines between the previous leg for the part of the segment that actually connects to the thorax.
Step 18: Use the initial circle and arc in the middle as guides to draw the thorax. Darken the outer edges of the guides to create the shape of the thorax. Don't overlap the legs at the bottom. Add a few curved lines within the shape of the thorax for the segments that correspond to the ant's legs.
Step 19: Use the remaining shapes as guides to draw the ant's abdomen the same way. Darken the outer edges of the guides to create the shape of the abdomen. Add a few lines inside the abdomen to create segments. Don't overlap the shape of the leg.