Is there such a thing as an official list of insect species found / sited in California?

and these are accessible via maps for species and genera available at www.discoverlife.org

I have consulted most of the obvious published sources (and very numerous obscure ones) and also obtained a very large number of unpublished records from examining and identifying specimens in collections (AMNH, Smithsonian, Cornell...) and from colleagues, notably Terry Griswold for the western USA and Sam Droege for the eastern USA. We intend to publish these records in print someday with appropriate documentation but in the meantime think it best to make them publicly available for use and review. Additions and corrections are much appreciated!

As for published sources on North American bee distribution, the standard references are Mitchell (1960, 1962) and Hurd (1979). The ranges cited in these works are highly incomplete, even for common and well known species.

"My" California list now includes no less than 1620 species and numerous additional records of species of uncertain taxonomic status or for which identifications are questionable.

California has far more bees than any other state. Many bee groups are well documented in the state, but not Nomada, Lasioglossum, Sphecodes, etc.

Papers on and a catalog of CA bees by Moldenke and colleagues are certainly worth tracking down.

...sort of thing when I first decided to finally get to know the local ants some years back. Since they're not the easiest insects to sort according to species, I decided to first contact our provincial museum of natural history, thinking they'd have some sort of official species checklist. Surprisingly, they didn't! Yes, they had quite a number of specimens museum staff had collected or which other folk had donated over the years, and a short-list of species which the museum biologists had officially identified by request for various government or commercial interests, but the sort of checklist I had in mind didn't exist yet for the ants of Nova Scotia simply because no one had ever bothered to study them. Hence my surprise. I'd always thought ants were amoung the 'cool' insects, the sort that would most attract the interest of budding entomologists/university students looking to undertake a project. :)

However, some orders of insects (moths, for example!) HAD already been well studied and the folks at the museum were able to provide me with their checklists plus lots of contacts, some of them general entomologists, others people with more specialized knowledge. So I imagine that's a good starter route for anyone right there...contact your state's/province's/region's biggest natural history museum(s) and then, by extension, the university entomology/biology departments, government deptartments, nature preserves, and even amateur naturalists they recommend. Insect checklists are out there, you just have to dig for them. And even if the insect order you're particularly interested in doesn't have a local species list available yet, there may be one for an adjacent state, province or region which'll serve as a helpful guide in the interim.

I can't give you an authoritative answer, just a few leads. The impression I get is that it depends on the taxonomic group, and on the potential local economic/ environmental role of the species: some, like lepidoptera and odonata, are avidly followed by hobbyists much as birds are.

Some specialists or organizations have compiled checklists and/or databases of California records for their areas of interest: Spiders, moths, and beetles, to name a few.

There are also national databases of certain groups like stoneflies that include county records for California among their coverage of all the US states.

Species that have the potential for serious economic or environmental damage are monitored by the state agriculture department or other agencies.

The rest are, perhaps, just informally tracked by specialists and by personnel at museums, etc.

Take a look through the resources I've assembled here for more details while we wait for a response from someone with more direct knowledge.