Disholcaspis prehensa
In 3 days ~10% in a week ~20%
Disholcaspis prehensa, also known as the clasping twig gall wasp, is a species of gall-inducing wasp. It is native to California, where it induces galls on both scrub oak and leather oak. The life cycle of Disholcaspis prehensa alternates between an asexual (agamic) generation and a sexual generation, producing two different types of galls at different seasons of the year.
In the spring, females from the previous sexual generation oviposit in young twig tissue, forming conspicuous mushroom-shaped galls which mature by early summer. The base of each gall has sharp edges and broadly wraps around the twig it rests on, giving rise to the common name, clasping twig gall wasp. The galls are 7–10 mm high and around 10 mm wide at the base. They tend to be more red in color on the sun-facing side, and more yellow on the shaded side, eventually browning with age. The larvae are housed in an elliptical chamber at the base of the gall, and they emerge from the sides as adults in late winter or early spring.
The adults that emerge are all female, and they reproduce parthenogenetically, laying their eggs into the dormant leaf buds of the California scrub oak. The new galls develop... Wikipedia →
| # | Park | Country | Daily sighting probability |
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More parks will be added in future updates.
| # | City | Country | Daily sighting probability |
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| 1 | San Francisco | 🇺🇸 United States |
Rare
Under 5% of wildlife watchers report a Clasping Twig Gall Wasp sighting in San Francisco on a given day, based on 85 verified sightings from GBIF citizen-science data. It is the 210th most-seen of the 737 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Clasping Twig Gall Wasp in San Francisco on a given day, so our monthly data shows no clear season.
Only San Francisco, in our data
San Francisco is the only city on Wallace's Line with enough records to rate Clasping Twig Gall Wasp sightings: under 5% of wildlife watchers there report one on a given day.
Same family: Cynipidae
The closest relatives of the Clasping Twig Gall Wasp that you can see in San Francisco (family Cynipidae, Gall Wasps) are California Gall Wasp (about 10%) and Live Oak Apple Gall Wasp (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Clasping Twig Gall Wasp is recorded against all the insects logged in San Francisco (85 verified sightings), 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.
