Andricus quercuscalifornicus
In 3 days ~60% in a week ~90%
Andricus quercuscalifornicus (occasionally Andricus californicus), or the California gall wasp, is a small wasp species that induces oak apple galls on white oaks, primarily the valley oak (Quercus lobata) but also other species such as Quercus berberidifolia, and Quercus garryana in Oregon. The California gall wasp is considered an ecosystem engineer, capable of manipulating the growth of galls for their own development. It is found from Washington, Oregon, and California to northern regions of Mexico. Often multiple wasps in different life stages occupy the same gall. The induced galls help establish complex insect communities, promoting the diversification in niche differentiation. Furthermore, the adaptive value of these galls could be attributed their ecological benefits such as nutrition, provision of microenvironment, and enemy avoidance.
The adult wasps are small, stout and brown, about 5 mm long with clear wings nearly twice the length of the body. The antennae are filiform and about the same length as the legs. Despite their size they are one of the largest species of cynipid wasps.
The gall itself is a typical oak apple gall in appearance, roughly spherical... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Channel Islands National Park | 🇺🇸 United States | |
| 2 | Joshua Tree National Park | 🇺🇸 United States | |
| 3 | Sequoia and Kings Canyon National Parks | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Sacramento | 🇺🇸 United States | |
| 2 | San Francisco | 🇺🇸 United States | |
| 3 | Portland | 🇺🇸 United States | |
| 4 | San Diego | 🇺🇸 United States | |
| 5 | Los Angeles | 🇺🇸 United States | |
| 6 | Seattle | 🇺🇸 United States |
Possible
About 30% of wildlife watchers report a California Gall Wasp sighting in Channel Islands National Park on a given day, based on 89 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 6th most-seen of the 131 insects we can rate there. Over three days the chance rises to about 60%, and over a week to about 90%, if each day is a fresh chance.
January and April
In those months about 40% of wildlife watchers report a California Gall Wasp in Channel Islands National Park on a given day, against about 10% in July, the lowest month. Those are among Channel Islands National Park's wettest months, with about 35 mm of rain a month against almost none in July.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most California Gall Wasp sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
Yes
Of the 3 parks where we can rate California Gall Wasp sightings, Channel Islands National Park has the highest daily chance: about 30%. Next come Joshua Tree National Park (United States, about 20%) and Sequoia and Kings Canyon National Parks (United States, about 10%).
Same order: Hymenoptera
The closest relatives of the California Gall Wasp that you can see in Channel Islands National Park (order Hymenoptera, Ants, Bees, Wasps, and Sawflies) are Yellow-Faced Bumble Bee (about 30%), Peridot Sweat Bee (about 20%) and Black-Tailed Bumble Bee (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the California Gall Wasp is recorded against all the insects logged in Channel Islands National Park (89 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
