The armyworm (Spodoptera exempta) is a very deleterious pest, capable of destroying entire crops in a matter of weeks. The larvae feed on all types of grasses, early stages of cereal crops (e.g., corn, rice, wheat, millet, sorghum), sugar cane, and occasionally on coconut. The armyworm gets its name from its habit of "marching" in large numbers from grasslands into crops. African armyworms tend to occur at very high densities during the rainy season, especially after periods of prolonged drought. During the long dry season in eastern Africa, population densities are very low. Because outbreaks are never observed during the dry season, it is called the "off-season" by those who monitor armyworms.