Diathrausta harlequinalis, the harlequin webworm moth, is a moth in the Crambidae family. It was described by Dyar in 1913. It is found in Mexico, Arizona, California, Colorado, Connecticut, Florida, Maryland, Massachusetts, Minnesota, New Mexico, North Carolina, Oklahoma, Ontario, Quebec, South Carolina, Tennessee and Texas. The wingspan is 13 mm. Adults have been recorded from March to October.