Spring! Texas Acmaeodera
As spring springs and as observations of Acmaeoderae are flowing into iNat, I wanted to give a quick synopsis-thing of the Acmaeodera found in Texas in spring--where the majority of Acmaeodera observations are focused, especially in March-April. This way, I might not have to explain differences betwixt species as often as I generally would. (I'd add pictures, but I actually only have seen two of the species listed below in person)
The Ornata Complex
The first 'complex' that exists is the ornata complex. This consists of Acmaeodera ornata and Acmaeodera ornatoides. The easiest way to distinguish this complex from the other one is size. The Ornata Complex is generally a centimetre or greater in length. It has almost white spots that are generally separated. For most people, the only species you will encounter in Texas is the latter (ornatoides). Acmaeodera ornata in TX is restricted to the extreme northern and eastern portions of the state and is generally fairly rare. This species can be separated from the more common ornatoides by the presence of a fairly distinct curved white line on the side of the beetle nearer to the head. Acmaeodera ornatoides, a much more common species, is restricted to TX. It can be distinguished by the lack of the pale 'humeral' line as well as the presence of a bluer sheen on the elytra.
The Neglecta-Tubulus Complex
The second 'complex' is much more complicated. This one is the neglecta-tubulus complex and contains Acmaeodera neglecta, Acmaeodera neoneglecta, and Acmaeodera tubulus (There are several other species in the complex, but they are either less common or not in TX). This complex can be separated by the size again since all species in the complex are about the size of a grain of rice--extremely tiny! Acmaeodera tubulus is widespread throughout TX and is generally identified by the presence of several large separated spots. It kindof looks like a tiny ornata if you squint. The second species is more of a species-complex within a complex. The neglecta complex obviously contains neglecta and neoneglecta. These two species are incredibly similar to one another--even their genitalia are almost perfect matches! This complex is highly variable and some individuals will have patterns near tubulus whereas others will look completely different! The only superficial way to differentiate between the two species is range at this point. As a rule of thumb, Acmaeodera neglecta is found north of Austin (the middle-ish of TX), and Acmaeodera neoneglecta is found south of Austin. Obviously this provides major issues, since both species will stray rather far from the Austin border and mess everything up. I generally will not ID species in the entire middle segment of TX to species if they belong to this complex, simply to avoid potential contradictions. However, 99 times of 100, the species in places like DFW and near will be neglecta and the species down in Corpus Christi and Big Bend to Val Verde will be neoneglecta.
Later in April, species from the pulchella complex--namely Acmaeodera mixta will make a grand appearance, but they are larger, yellow-browner, and much scarier to figure out.
Other spring species, uvaldensis, miliaris, tildenorum, starrae et cetera are much more rare and restricted to areas such as S or W TX. I'll not really address those, since the majority of people will never encounter any of these species.
And that's it! Just 4 common species to learn (or maybe 5...6...7...maybe 10...just kidding). Hopefully, this will be helpful--it was helpful for me since I had nothing better to do with the past couple hours of my life.
Oh and this can basically apply to most east coast states with a few changes: only species are neglecta, tubulus, ornata, and now pulchella. Pulchella has yellow spots, so there's no way that can be confused with these other brown-white dotted species.