10 August 2026
In August in southwestern PA you may notice a tiny white ball floating above the trail, maybe at eye level. If you walk into it you discover the ball is on a thread. It moves horizontally in a light breeze and can raise and lower itself. On closer inspection you can see it’s a white insect.
The white balls are the caterpillars of the planthopper parasite moth (Fulgoraecia exigua), one of the very few carnivorous moths in North America. The species is not rare but its dietary habits are.
In a super-closeup the tiny caterpillar looks like this.
The adult moth is also tiny with a wingspan from 8-13 mm (0.3 – 0.5 inches).
Since their life cycle is not tied to a host plant, the female lays her eggs on any vegetation where her young will find planthoppers to parasitize. Perhaps she chooses a site where planthopper nymphs are already present.
When her eggs hatch the tiny caterpillars seek an adult planthopper, latch onto it under the wing, and proceed to suck all the juices out of it. Here’s an example of what they’re looking for, the most common green planthopper in PA: Acanalonia conica the green cone-headed planthopper.
Two closeups from iNaturalist show the caterpillars actively parasitizing green planthoppers.
Planthopper is green and is facing downward.
Planthopper is facing right.
Eventually this sucking of body fluids kills the planthopper. The caterpillar drops off and, when it’s ready to pupate, it drops from the trees on a silk thread to find a place to make its cocoon.
The shape of the tiny cocoon is unusual. Brandon Woo of The Incorrigible Entomologist likened it to the Sydney Opera House in 2018. That’s what everyone calls it now.
Eventually the moth emerges and the cycle starts again.
Watch for a tiny white ball on a thread this month. It’s Bug Season!