Coniontis spp.

This caresheet should be applicable to most Coniontis species, but there may be a few exceptions of course.
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Housing:

Any container about gallon in size, with more width than depth, (but still with at least 3-4 inches of depth) will work well for a starter colony, and you can upgrade the enclosure size a bit as their population grows. None of the life stages can climb, so a tight fitting lid is not necessary.

For the substrate, coconut fiber or a mix of coconut fiber and sand should be provided, you can mix in other organic matter as well, just be sure not to make it too coarse. On top of the substrate should be a layer of dead hardwood leaf litter, which seems to be an important part of their diet. (All leaf litter should sterilized, so as to avoid nasty fungal pathogens or mite infestations). No hides are needed for this genus, both adults and larvae spend almost all their time underground, their substrate provides them with all the cover they need. 

Most of the main enclosure should be kept very dry, with a third or so of the substrate being kept moist at all times. You can go with a horizontal humidity gradient, or, if you have enough substrate depth, a vertical humidity gradient, (which would probably allow for more larvae to pupate in the communal enclosure successfully). They should be given a very high amount of ventilation, as per usual for desert/scrubland dwelling Tenebrionids, in fact you could probably get away with keeping them in a lidless enclosure, provided the substrate is an inch or two below the top of the container.

Diet:

Decaying hardwood leaves make up a large portion of their diet, and they also really enjoy dog/cat/chick feed. Most fruits and veggies usually go ignored, but some root veggies may be accepted.
I suggest using shallow food bowls for this genus, so that they don't drag it all underground, which can make removing leftovers a pain... 

Temperature:

They breed well at temps from 70-76F°, any higher might result in a slight to high larval die off.

Breeding/Life cycle:

Adults live for 9-12 months, it's hard to tell just how long when you've got a good sized colony with overlapping generations, and I can't recall any of my adults living more than a year. Females lay dozens of eggs during their lifespan, which are very large in comparison to their bodies and oval in shape. The eggs take less than a month to hatch, and the resulting larvae take 6-8 months to mature, then create a pupal cell and enter the pre-pupal stage for approximately 1-2 weeks. Then they molt into a pupa, and typically in less than a month they will eclose into a soft, teneral adult.

Ideally, in a large enough enclosure with a proper humidity gradient, larvae will successfully pupate and mature in a communal setup. However, if for some reason there are too many individuals in the enclosure, or the enclosure is too small, has an improper humidity gradient, etc., you may need to isolate larvae yourself to induce successful pupation. 

To do so, remove fully grown larvae from the main enclosure and isolate them in 2 oz deli cups with minimal ventilation, and an inch or two of moist, compressed coconut fiber, or a coconut fiber and sand mixture, (adding some sand to the mix may help their pupal cells keep their shape). Leave them be and don't feed them, just make sure the substrate stays moist, but not wet.
It may take a while for the larvae to decide to pupate, and some may die before doing so, however the survival rate during this period and of the pupae is pretty high in comparison to some related genera.

After the adult beetles eclose and darken up a bit in color, they usually dig their way to the surface. They should immediately be removed from their humid deli cups, and can either be isolated in a "hardening" container with mostly dry sand substrate and a moist corner, or they can just be placed back into the main colony right away. The benefit of keeping them isolated while hardening is that they are less likely to be stepped on by their tankmates in their teneral state, causing permanent dents and such in their soft exoskeletons.
However, the adults of this genus have rather thick and sturdy exoskeletons even when teneral, and since they spend most of their time underground, it's usually safe to place teneral individuals right into the main colony after they've turned a dark orange color.

If grain mite infestations occur on account of the beetles dragging food underground, simply feed less grain based foods for a while, and keep them a bit drier than normal until the mites go away.

The species I've kept never needed a diapause during the winter, but it's possible some other species may require a cool period during winter.

These little beetles are quite interesting little US natives, and seeing as the genus is rather widespread, I hope they become more popular in culture as time goes on!