Bug FAQGrass Demon
Udaspes folus · Order: Lepidoptera · Family: Hesperiidae
Source: Wikipedia
It lives in deciduous and semi-evergreen forests across South and Southeast Asia, favoring the edges of open spaces and is most often seen during the monsoon season. The caterpillars feed on ginger, turmeric, related plants and sometimes grasses, and can become occasional pests of these crops.
Source: Wikipedia
How to recognize it
It displays a unique wing-flashing motion right after landing on a leaf.
Source: Wikipedia
Size
Its wingspan ranges from about 4 to 4.8 cm.
Source: Wikipedia
Where it lives
It inhabits deciduous and semi-evergreen forests.
Source: Wikipedia
What it eats
The larvae feed on ginger, turmeric, Curcuma species, Hedychium, and other members of the Sctiaminae family. They have also been recorded on Zingiber species and on grasses.
Source: Wikipedia
Life cycle
Adults emerge in February or March, lay eggs and then die.
Source: Wikipedia
When you see it
The butterfly is most commonly seen during the monsoon season.
Source: Wikipedia
Where it comes from
It is native to Sri Lanka, India, Nepal, Myanmar, China, Indochina, Taiwan, Japan, Thailand, the Malay Peninsula, Singapore, Borneo and Indonesia.
Source: Wikipedia
Lookalikes
No other peninsular Indian butterfly can move its forewings and hindwings separately, making this a distinctive feature.
Source: Wikipedia
More photos
Questions people ask
Is the grass demon harmful to my garden?
Yes, its caterpillars can damage ginger and turmeric plants, making it an occasional crop pest.
Source: Wikipedia
When am I most likely to see a grass demon?
You will most often see it during the monsoon season.
Source: Wikipedia
What does the grass demon look like?
It is a small black butterfly about 4 to 4.8 cm across, with a large white spot on the hindwing upperside, smaller white spots on the forewing, and a mostly white underside with brown edges.
Source: Wikipedia
Where does the grass demon live?
It inhabits deciduous and semi-evergreen forests across South and Southeast Asia, preferring forest edges.
Source: Wikipedia
Same family (Hesperiidae)
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Ancistroides_folus
Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia
Text written 2026-10-24 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.