31 August 2026
A week ago at Hays Woods I found a nest of fall webworms (Hyphantria cunea) at eye level. We usually see these webs high in the trees so this was a good opportunity for a closer photo, shown above.
Their mother had laid a mass of eggs on a leaf; a week later the eggs hatched into tiny caterpillars. To protect themselves they built a communal web, mostly at night, to surround themselves and the leaves they are eating. As they consume the leaves they expand the web. As ugly as this looks it does not harm deciduous trees because this is the end of the growing season.
Fall webworms stay close to each other when they’re small but at the 5th or 6th instar they venture out alone. In this photo from Bugwood, the tiny ones are inside.
To get a better photo of the caterpillars I approached the web. In response they began a strange and jerky distraction dance.
If I was a warbler would I be thrown off by this display? Or would I eat a worm anyway? If I was a yellow-billed cuckoo I’d probably pluck a webworm as an easy meal.
The webworms that survive pupate into a 2-inch moth. Males are speckled, females are all white.
