https://forum.inaturalist.org/t/how-complete-is-arthropoda-on-inaturalist/57838/5
The first thread I made about this topic can be viewed here, I wont try to retread previous ground too much here.
I decided to update my dataset. I got as many updated species numbers for arthropods I could, though keep in mind I couldn’t find updated definite species numbers for mite orders or the major insect orders, so these are likely to be under estimates. I of course also updated the numbers of observed species and observations. And I added several more parameters as well. In addition to total known species, observed species, observations, and percent of known species observed, I also added numbers of research grade species, research grade observations, percentage of observed species that are research grade, percentage of observations that are research grade, and percentage of total known species that are research grade. The stats for arthropod as a whole look like this.
Total known species: 1,247,491
Observed species: 237,817
Percent of total species observed: 19%
Observations: 71,394,654
Research grade observed species: 193,568
Research grade observations: 39,579,246
Percent of observed species research grade: 81.39%
Percent of observations research grade: 55.4%
Percent of total species research grade: 15.5%
The percent of total species observed has remained largely the same, because the increase of species observed on inat was made up for the fact many new species were described (both via novel discoveries and taxonomic revisions). It is likely to be less than 19% because, again, I did not account for the increase in species of mites and the 4 big insect orders.
Lets first mention first the the orders with no observations. Platycopida, Thermosbaenacea, Misophrioida, Platycopioida, Mictacea, Palaeocopida, Gelyelloida, and Siphoniulida. Next are the orders with observations, but none of which are research grade. Canuelloida, Bathynellacea, Acrothoracica, Stemmiulida, Ascothoracida, Mormonilloida, Cephalocarida, and Tantulocarida. All but two of these orders are various rare, obscure crustaceans. Two are millipede orders. The reasons for why these crustacean taxa are so poorly represented are covered in greater depth on my original post.
Now, lets see who are the winners in each of the new categories
The orders with the largest number of research grade species are those with the most species in general, or have substantial numbers of large, easily identified species. Nothing really special here.
Same thing for number of research grade observations. Either orders with the most biodiversity in general, or those made up disproportionately of large bodied or easy to find species.
Now, this is where things get a bit interesting. Most of the 3 orders with 100% completion, xiphosura, craterostigmomorpha, and cyclestherida also have 100% of their species research grade, because they have so few species to begin with. You then have a bunch of rare, obscure taxa that have very few of their species observed, but those that are observed are all research grade because they likely all observed and identified by specialists in those taxa. These include remipedes, stygiomysids, palpigrades, opilioacarids, mystacocarids, and holothyrids. The highest percent of research grade among observed species in orders with decent sample sizes are among earwigs, scorpions, stomatopods, odonates, mantids, and amblypygids. Odonates stand out as being particularly well sampled, having both a majority of species observed and a vast majority of those species having at least on research grade observation.
Now this is really interesting. Remipedes are the only order where 100% of observations are research grade. Remipedes have been observed by 3 people on inaturalist, all of which seem to be specialists. You can also see other obscure taxa like strepsipterans and spelaeogriphaceans have fairly high percentages of research grade observations, again because of low sample sizes and specialists are likely to be the only ones to even be able to find/notice these animals in the first place. Of course, the highest percent of research grade observations that aren’t based on tiny sample sizes are the odonata, at around 81%.
And finally, we have research grade species as a percentage of total species. Aside from the three orders above that each have very few species mentioned above, the most well sampled orders in this category are the notostracans, pollicipedomorphs (gooseneck barnacles), and megaloptera (dobsonflies and alderflies). These taxa have the unique combination of having modest species counts, large body size, easily observed, and not that hard to identify. Of course, odonata are near the top too. It’s worth noting that odonate is on the same level of completeness in this category as the previous three orders despite having way more species.
Of course, this should all be taken with a grain of salt, because many inat identifications (even research grade ones) may not be accurate, and species numbers are changing. Let me know your thoughts in the comments