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 20% of wildlife watchers report a California Gall Wasp sighting in Joshua Tree National Park on a given day, based on 120 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 19th most-seen of the 190 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.
December and January
In those months about 40% of wildlife watchers report a California Gall Wasp in Joshua Tree National Park on a given day, against under 5% in August, the lowest month.
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.
2nd of 3
Of the 3 parks where we can rate California Gall Wasp sightings, Joshua Tree National Park ranks 2nd at about 20%. The best odds are in Channel Islands National Park (United States, about 30%).
Same order: Hymenoptera
The closest relatives of the California Gall Wasp that you can see in Joshua Tree National Park (order Hymenoptera, Ants, Bees, Wasps, and Sawflies) are Messor pergandei (about 30%), California Harvester Ant (about 30%) and Rough Harvester Ant (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 Joshua Tree National Park (120 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.
