Wikipedia
Opisina
Opisina arenosella, the coconut black-headed caterpillar, is a moth in the Xyloryctidae family, and the only species in the genus Opisina. It was described by Walker in 1864 and is found in India, Sri Lanka, Bangladesh and Myanmar.
The wingspan is 10-15 mm. Adults are grey.
The larvae are gregarious and are serious pests of coconut trees. They defoliate their host plant.