Dealate on piece of wood.
At night in granite ravine of desert Larrea, Fouquieria, Cylindropuntia shrubland. Rained in preceeding days.
Appears to have erect/suberect setae on dorsal surface of hind tibia, and mexicanus is most common member of the Myrmecocystus subgroup here.

Pamillia behrensii plant bug (Miridae), Izaak Walton Park, Bishop, Inyo County, California - 15 March 2015. The bug (on the right) was a very effective ant-mimic, here shown with its models, two different castes of Liometopum occidentale (Velvety Tree Ants, maybe worker and soldier?). These insects were brushed from a tree trunk, photographed on my beat sheet and then released. M.D. Schwartz was kind enough to identify the mirid to species and James Trager was kind enough to identify the ants. More details and photos here: bugguide.net/node/view/1047081

Large number of adult male and females on Rhus integrifola shrub foliage at dusk. Multiple females were observed ovipositing on flower buds(images 2-4) and pupal exuviae were also present (images 5 and 6).

Update May 2021: Photos and info gleaned from this occurrence used in the Wikipedia article I wrote for this species:
https://en.wikipedia.org/wiki/Ornithodoros_coriaceu

This thing truly weirded me out. Like a tank-tick. Big. Gross. And after doing some research I am DAMN glad it did not bite me.

"George Henry Falkiner Nuttall - Monograph of the Ixodoidea

Two females bit Mrs Z Nuttall through her clothing and inflicted painful wounds, "their ites were intolerably sharp and painful, and both wounds bled a good deal – but notwithstanding, there has been intermittent irritation ever since" (this persisted after 4 months, and the seat of the bite was stil discolored and the puncture covered by a scab). Eight months after the bite was inflicted, there remained a nodule which occasionally itched. The natives of Tehuantepec, Mexico fear this tick for the reason that the bites are severe and often do not heal for a long time. The females immediately proceeded to feed, on arrival in Cambridge, when placed upon a fowl. They fed for 45 minutes and 1 hour and 45 minutes respectively, and drew a large amount of blood. The bites caused intense ecchymosis, measuring about one inch in diameter. Whilst feeding the palps did not penetrate the wound as once observed in the case of O. savignyi, but both specimens exuded clear fluid as observed in O. moubata."

From Furman and Loomis' Ticks of California:

"0. coriaceus was originally collected in Sonora, Mexico, and is distributed in the other western states of Mexico southward to
the Isthmus of Tehuantepec, where the natives call this tick "talajas" (tala = destruction, havoc). Berlese (1888) states
that he saw a specimen taken from cattle hides at Rio Apa, Paraguay. From 1904 185-1850 m elevations along the coast from
through 1941 numerous collections of this species were made in the coastal regions of California (Cooley and Kohls, 1944b), and intensive surveys in subsequent years have shown that this tick is widespread in California and occurs in Nevada and southern Oregon (Loomis and Furman, 1977). Originally called "pajaronela" by the inhabitants of the Santa Lucia mountains.

The pajahuello is best known because of the severe reaction in humans following exposure to its bite. Initial bites usually result in a localized inflammatory reaction accompanied by a burning sensation and a small nodule that forms around the wound.

These symptoms usually disappear within 48 hours, leaving a small, purplish nodule that disappears in 1-2 weeks. In other cases, an umbilicated pustule surrounded by an inflamed, painful, edematous area develops. More severe allergic reactions appear in persons previously bitten and thus sensi- tized to a substance injected during the tick's blood-feeding process.

1. coriaceus is not known to transmit any disease of man, but on the basis of circumstantial evidence it is capable of transmitting the agent of a cattle disease called epizootic bovine abortion ("foothill abortion") (Schmidtmann et al. , 1976), and has been shown experimentally to transmit African Swine Fever virus to healthy pigs (Groocock et al., 1980)."

From Herms, 1916:
"
For several years previous to beginning his observations on this
species, the writer has listened to many harrowing tales about the
Pajaroello. No one seemed to know exactly what it was and no one
seemed to have collected specimens so as to make accurate identification
possible in so far as the writer knew at the time. Complaints came
almost exclusively from the more mountainous portions of Santa Clara and San Benito Counties (California). Natives, principally Mexicans, in the vicinity of Mt. Hamilton fear this parasite more than they do the rattlesnake, and tell weird tales of this or that man having lost an arm or leg, and in one instance even death having ensued, as the result of a bite by the Pajaroello. There seems to be a superstition in that region that three bites will result in certain death. The stories all agree in the essential detail that the bite results in an irritating lesion which is slow to heal and often leaves an ugly deep scar. Several persons also informed the writer that the Pajaroello occurred in certain mountainous portions of Mexico. It was not, however, until August, 1913,
that living specimens came to hand, taken in Santa Clara County in the vicinity of Mt. Hamilton. These were identified as Ornithodorus
coriaceus Koch, described in 1844 from a single female specimen from
Mexico. A translation by Nuttall of the original description is as follows:

"Shaped like the sole of a shoe, thick margined, roughly shagreened, yel- lowish earthy color, spotted rusty red, legs toothed dorsally. Length 9.3 mm. Body about twice as long as wide, width fairly uniform, indented on the sides, pointed above the mouthparts, rounded posteriorly, a thick turned-up border all around; the whole surface above and below thickly granulated like fish
skin (shagreen), the granules flat above, consequently, the whole leathery, on the back unequal folds and grooves. Beneath in the front of the body a deep groove running to the stigmata and on the inner protrusion the rather large round quite clearly marked eyes. The coxae gradually thicken toward the distal extremity and are somewhat bent; the other articles somewhat com- pressed and clearly notched or round-toothed. The whole surface, above and below, dirty yellowish earthy color, rusty red spots irregularly distributed throughout. Capitulum and palps light yellow. Legs gray-brown. Female. Male: unknown. Habitat: Mexico."

Growing with Caloplaca subpyraceella on old rabbit and rodent droppings on open sandy soil with bryophyte, liverwort, and cladonia mats. In Adenostoma, Arctostaphylos, Artemisia, Baccharis, Yucca shrubland.