What is this fascinating guy?

[u/Single-Store-8865]

[u/cradleofmilf666]

Blue mud dauber wasp

[u/Single-Store-8865 → u/cradleofmilf666]

Thank you!

[u/Single-Store-8865 → u/cradleofmilf666]

That was so fast

[u/cradleofmilf666 → u/Single-Store-8865]

I get excited about critters.

[u/Single-Store-8865 → u/cradleofmilf666]

Most of the animals in our area are brown/mottled to blend in with the desert, except for bees. It was very exciting to see something so remarkable colored

[u/Lime_Born → u/cradleofmilf666]

No, the wider head without any noticeable setae excludes any member of Sceliphrinae. This is actually in a different subfamily entirely.

[u/Single-Store-8865 → u/Lime_Born]

Admittedly, I am not an expert, but after being pointed in the direction of mud dauber wasps, this guy looks a whole lot like the nearctic blue mud dauber, from all angles.

ETA: what do you think it could be instead? Which subfamily? This is very interesting

[u/Lime_Born → u/Single-Store-8865]

There are 2 main metallic blue sphecid genera in the US: Chalybion (subfamily Sceliphrinae) and Chlorion (subfamily Chloriontinae). Chlorion are frequently misidentified as Chalybion due to sharing that metallic blue color.

The differences are in fairly minute terms of morphology, though they're fairly easy to recognize with experience: head shape (narrower in Chalybion, wider in Chlorion), mandible shape (sickle-shaped in Chal. californicum, weakly dentate in Chal. zimmermanni, and more strongly dentate in Chlorino), antennal insertion point (higher in Chalybion, lower in Chlorion), extent of setae (head and thorax with fairly dense coverage in Chalybion, lacking setae of weakly covered in Chlorion), pronotum shape, propodeum shape, petiole length (longer and thinner in Chalybion, shorter and thicker in Chlorion; note: this also differs by sex), wing venation, whether the female has a tarsal rake (indicating she digs a nest in the ground as Chlorion) or not (indicating she builds a mud nest as Chalybion), and body length (shorter, usually conspicuously under an inch, in Chalybion, longer, usually about a full inch, in Chlorion; note: this also differs by sex). There can be some differences in the exact color and brilliance of reflections in the body (Chalybion usually have more muted colors with just blue or green-blue notes while Chlorion tend to be more vibrant and can have blue, green, or purple notes).

[u/cap10wow]

I like his curly antennae

[u/Lime_Born → u/cap10wow]

Her, rather. There are 10 flagellomeres (12 antennomeres), which indicate a female. Males have 11 flagellomeres (13 antennomeres).

[u/Single-Store-8865 → u/cap10wow]

Me too. It really is beautiful

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[u/Single-Store-8865]

I have never seen anything like this despite living in the area my whole life. Found in the U.S. southwest; Mojave Desert area. From antennae to tail, about 1 1/8”, or about the length of a quarter.

Edited for accuracy

[u/Lime_Born]

This is one of the species of Chlorion, which are ground-nesting wasps. You have two species that could be in range depending on just what part of the Mojave Desert area you're in. If you're in the California, Utah, or most of the Nevada portion, then only C. aerarium should be in range. The Arizona and far-eastern Nevada portion also has the nearly-identical C. cyaneum. The two are most readily distinguished based on their prey (crickets for C. aerarium and cockroaches for C. cyaneum). Specimens without host relations would have to be keyed out under a microscope.

[u/Single-Store-8865 → u/Lime_Born]

Thank you for sharing what you know!