Top. A horizontal asymptote is a y-value which a function approaches. The asymptote is parallel to x axis, so is of the form y = a, for all real values of a. Thus if f(x) = y is a function, then y = a, becomes undefined for the function, then the line y = a, is called the asymptote for the function y = f(x).
The African armyworm (Spodoptera exempta) also called okalombo, kommandowurm, or nutgrass armyworm, is an African moth. It is a very deleterious pest, capable of destroying entire crops in a matter of weeks.
1 An increase of the number of birds in your yard may be an indication of armyworms. Birds eat the caterpillars, but usually do not eat enough of them to keep the infestation under control.  Brown spots on your lawn are often the first sign that you have an armyworm problem.