in damselflies, "ischnura", females are frequently harassed by males that wish to mate. there is significant variation in the females’ physical abilities to tolerate male mating harassment. in this species, there is a physical dimorphism: one type is cryptic (heteromorphic) and the other type looks like a male (andromorph). in many cases the andromorph even behaves like a male when among other males. studies have found that the andromorph only mates half as often as the heteromorph. while a decrease in mating would be devastating for males, it is often an advantage in females. for females, excessive mating is a waste of time and energy and it increases exposure to predators. thus, the ability to ward off extra mating gives the andromorphs a frequency dependent selective advantage. this is example of a traditionally male characterized mendelian alternative strategy that has now been observed in females.