Oidaematophorus beneficus

The wingspan is 22–28 millimetres (0.87–1.10 in). Adults are on wing in February and July, at an altitude of 450 to 1,350 metres (1,480 to 4,430 ft). The moth prefers higher altitudes and has rarely been observed below 460 m (1500 ft) by researchers in Hawaii. The larvae feed on Ageratina riparia. Pupation takes place on leaves or in litter at the base of the plant or on the stem. The moth larvae create smooth edged holes in the plant's leaves, which stunt its growth. Because the A. riparia is highly invasive in tropical climates, the moth has been used as a biological control agent to slow its growth. Although the larvae are highly specific to A. riparia, they have also reportedly been found feeding on A. adenophora in Hawaii. The parasitoid wasp, Meteorus laphygmae has been observed parasitizing the species' larvae in Hawaii.

H. beneficus is native to Mexico, in the region which its larval host plant, A. riparia originates. The species of moth has since been introduced to other regions as a biological control agent against A. riparia. After collecting specimens from Mexico, unsuccessful attempts were made to introduce the species to Hawaii in 1959 and 1965. The moth was successfully introduced in Hawaii in 1973 when a total of approximately 1525 specimens from Contreras, Mexico were released at Mt. Kaala and Kona.