Cobweb[x_, n_, A_] := Module[{a, b, CobList, CobList2, f},
  f = (-A #^p Log[#] &) /. {p -> 6/5};
  CobList = NestList[f, x, n];
  CobList2 = Append[Rest[CobList], f[CobList[[-1]]]];
  a = Partition[Append[Riffle[CobList, CobList2], {0, x}], 2, 1];
  b = Plot[f[y], {y, 0, 1}];
  Show[ListPlot[a, Joined -> True, PlotStyle -> Red], b,
   Plot[y, {y, 0, 1}]]]
Cobweb[.4, 50, .56]