Withered mocis, photographed in northwestern Delray Beach, Palm Beach County, in August 2021.
The withered mocis, Mocis marcida, isn’t a moth you want to see fluttering about your lawn. It isn’t the adult moth itself that’s the problem. It’s the kids, the larvae, also called grass loopers or striped grass worms, that are the problem.
Why? Because they eat grass. Grass for breakfast, lunch and dinner, and grass for snacking in between. Your lawn. Your pasture. Their meal.
To be fair, spotting one or two withered mocis probably isn't a cause for panic (as in Panicum. Botanical pun. Our sincere apologies). Seeing more of them and your yard is looking a little patchy, then you might want to take a closer look.
Withered mocis are one of three members of the genus Mocis found in Florida, all of which are similar in looks and habit. And all can be major pests particularly to cultivated and wild grasses.
Adult withered mocis are medium-sized, with a wingspan of about two inches. Overall, they are a dull brown or purple-brown. The edge of the forewings are dark brown, becoming lighter farther in, with a series of dark cells or spots. All three members of Mocis are similar in their looks and can be difficult to tell apart.
Withered mocis are mainly found in the southeastern United States, roughly from North Carolina south to Florida and west to Texas. There are records of these moths flying as far north as New York, but they are rare. They also range south through the Caribbean, with sightings in Mexico, Central America and South America.
Favored habitats include fields, marshes and open, grassy areas.
Grasses are the host plant for the withered mocis, and therein lies the problem. Larvae, be it moth or butterfly, eat their hosts. In sufficient numbers, these grass loopers can inflict considerable damage to a lawn or a pasture.
The larvae have dark and light stripes running the length of their bodies and look a lot like dead grass, allowing them to blend into the scenery and avoid predators. They also play “possum” when a predator approaches. Instead of wriggling, they drop to the ground and play dead.
Withered mocis are members of Erebidae, a large family of moths.
