With a wingspan of 5 to 6 inches, the cecropia moth (Hyalophora cecropia) is the largest North American moth. It is a member of the family Saturniidae. Cecropia moths are often referred to as silkworm moths.Although these moths are common throughout North America, you don't often see them because they fly only at night. However, because a cecropia moth is colorful as well as large, when you do see one for the first time, you won't forget it! Like most moths, they are attracted to bright lights. This is where most people see them for the first time.