The Desert turned yellow

The Common Cinchweed, Pectis papposa, is back. In the nineties and early two thousands, the yellow blooming little Asteraceae used to carpet the desert, and perfume the area with their Chamolmile-like scent, each summer after the first heavy rains.

I have photos of all my old dogs, who accompanied us in those years, surrounded by seas of yellow. The appearance of these summer wildflowers was actually more reliable than that of the spring bloom which requires a complex pattern of autumn and winter rains. Sadly, this summer exuberance ended when the draught hit several years ago. The desert floor between cacti and creosote bushes remained bare for many years. But it kept the seeds safe (seed bank)! All it took was a good drenching and sprigs of green popped up, within days forming a dense carpet. Each multi-branched plant is only as big as a hand and about that high. The Chinchweed plants are interspersed by pale green cheat grass plants that bloomed so quickly that they are already setting seeds. In some years the balance was shifted and the grass was dominant, but this year it's definitely the Chinchweed. All that yellow is interrupted by silvery gray patches of a ground-hugging little Euphorbia.

So many odorous flowers should be attracting many pollinators. If they are small bees and flies, they would be easily overlooked in this ocean of yellow. More obvious are butterflies. We just had a great influx of all kinds of Sulphurs, so those are dancing over the flower-fields in great numbers. Whites are rarer.

There are also Variegated Fritillaries and Queens, and of course American Snouts by the hundreds. This morning I saw the first White-lined Sphinx racing around, but I could not tell if they were nectaring on the Cinchweed or on their way to some Datura or Devilsclaw flowers that are now waiting for pollinators along the washes.

Yesterday I discovered an interesting phenomenon: after a cool morning with lots of butterflies on the flowers, the temperatures had risen to above 100 Fahrenheit and much fewer butterflies were to be seen. But when I accidently walked close to a Creosote bush at least a dozen Sulphurs of several species flew up. So I tried some more bushes with the same result. The butterflies were sitting with their wings tightly folded, obviously waiting out the midday heat in the shade of the bushes. I had never thought much about the thermoregulation of butterflies beyond their obvious attempts to warm up in cool weather by opening their wings and orienting them towards the sun. I am, after all, a child of the very temperate climate of Geermany. But I took the hint from those Arizona natives and quickly withdrew into the shade, actually into the cooled house.

Where are the bugs of Mount Lemmon?

Yesterday, Randy and I took Chaco for a walk high in the Catalina Mountains, above Ski Valley, so above 8000 feet. It was refreshingly cool with a big cloud accompanying us most of the way. We gladly accepted the shade, because Meadow Trail first loses a lot of elevation in narrow switch-backs which we had to regain later on Mount Lemmon trail.

We are very happy that Chaco has overcome his old insecurity. He used to bark and growl at strangers who suddenly appeared, humans and dogs alike. He likes most humans now. A treat can convince him that most dogs are okay as well. It took him a good a year with us to gain this confidence, but it happened over the course of 2020, during a year of nearly complete isolation. So actively socializing a dog is not necessarily the only way to train a dog to be accepting of and friendly to strangers. Interesting

The landscape is still wearing scars of 2 big fires of the last decade. After some real gushers last week, scars from flood-erosion are also obvious. Still, forest and meadows are gloriously green and studded with wildflowers. I got the impression that some, like Gilea and Verbena, are blooming late this year, so they are adding their pinks and purples together with wild Geraniums, New Mexican Thistles and Cornflowers to the yellows of Golden Columbine, Sneezeweed and Golden Route. Path borders are accented by the deep blue of Day Flowers and the red of Penstemon. Very pretty also a blue-blooming night shade with leaves like a potato plant. Spotted Horsemint, Monarda punctata, stood out in big healthy clumps. More pale pink or white of fleabane, and Common Yarrow.

With so many wildflowers, we expected to find interesting insects. A Yellowjacket joining us at our early lunch in the picknick area seemed promising. And butterflies, mostly Sulphurs and some Queens, were in the air, some few Painted Ladies on flowers. White-lined Sphinx buzzing like Hummingbirds. A few Honey Bees. But no Bumble Bees, no Longhorn Bees, the only beetles were tiny Dasytine Melyrids. Hardly even any Bee Flies. No big wasps and Carpenter bees on the inviting stands of Monarda – nothing.

A sad little group of 5 Convergent Ladybugs on the tip of a Sneezeweed leaf. There used to be thousands on the mountain at this time of the year (I hope I just missed the right spots?). When we got back to the car, I made a last effort using my beating sheet. Randy and Chaco went into hiding. Around the trailhead parking lot are stands of Aspen and mixed conifers. I always found Interesting Ladybugs, Weevils, the occasional Longhorn (Neoclytus) and many spiders in my sheet. This time I got nothing from the conifers and one Mirid and some ants from the Aspen. It was quite discouraging. Before we got into the car, I finally photographed a single Syrphus opinator that was hanging out on an Aspen leaf

On the way home I was trying to convince myself that the low temps on the mountain top had driven the insects into hiding, so we stopped to admire 2 amazing, pink blazes of Mallow at Middle Bear at medium elevation, before continuing to Molino Basin. Low enough for some desert vegetation to thrive, but still supporting several species of oaks along the creek (running brown with tannins) Molino Basin is usually rich in insect species. But this time I learned why bind weed, or morning glory, has such a bad rep in Arizona that most species are prohibited in commercial sales (we had always found that restriction quite ridiculous).

But at Molino, in August 2021, you’d quickly understand. Bush after bush of Mazanita, small oaks, Desert Broom and even fast growing, freshly sprouted Datura were completely covered in a thick suffocating layer of Bind Weed. Not all were in bloom, but from those very lush and intricately lobed leaves I could tell that at least 4 species of Morning Glory were involved. Surprisingly, the delicate Scarlet Creeper, Ipomea coccinea contributed a lot to the chaos. So no Euphoria and Longhorn beetles on those Desert Broom bushes. Just a lot of flies (house flies?) that got into our car. Maybe even they had decided to leave the mountain.

A Sub-optimal Pollinator

Honey Bees and the Datura spp of the New World did not evolve together, though there are Datura spp in Eurasia where the HBs originated. Still, the architecture of the long-throated flower, it's mostly night-blooming ways and its color point to moths as it's pollinators, and among these, the 'long-tongued' Sphinx moths are the obvious candidates. But then, if you catch a Honey Bee you may get pollinated anyway! On its way in, to get nectar, the bee passed the loaded pollen sacs, and while it fights to escape the entrapment by the slippery walls of the narrow throat it probably comes in contact with the critical parts of the stigma. So pollination may happen. Speculation: Does the bee seem unusually clumsy? Did the alcaloids of the plant give it a buzz that may make it stumble around the floral sex organs just a little longer? I cannot find conclusive data about the effect of those phytochemicals on the neural system of insects This is Datura discolor, one of three species in the Tucson area. They are only now starting to bloom, while the Datura wrightii (sometimes called sacred datura) has been blooming for a couple months or more. D. discolor has the purple throat markings, D. wrightii is white.

Why do the Caterpillars Cross the Road

Why do those caterpillars cross the road? I think this question is usually caused by avealanches of White-lined Sphinx caterpillars. The do cross the road in search of more food. Their eggs seem to be laid in clusters, while many other sphinx moths distribute them one by one. WLS caterpillars feed on small herbs (many kinds, but still selectively) So they can exhaust that resource in one spot and then they have to move on. The photo by David Bygott illustrates that well. Another possibility would be that they are all on their way to pupation, away from dangerous feeding grounds that attract predators and towards better soil to dig into (Carl Olson suggests this). But I have seen many different sizes wander together, and also found them munching happily again when they found more food plants. It's probably the unexpected sterility of the road that makes the migration so obvious and determined.

On the other hand, a Manduca caterpillar (here Manduca rustica on cape Honeysuckle) for example, will not have to share with as many siblings, the eggs being more spread out by the female. Also, a caterpillar that feeds on tree leaves, or even on bigger annual plants like Datura will not easily exhaust that resource, so we rarely see those hornworms wander around before they are ready to find a pupation spot away from their original host plant.

The strategy of sudden mass-production by the White-lined Sphinx is a desert adaptation that seems to work extremely well, even though many horrified drivers on our highways notice the inevitable slaughter of many of those road-crossing caterpillars. WLS are able to capitalize very quickly on sudden bursts of annual-plant growth that sporadic heavy rains produce in the desert.

My black-lighting sheets are sometimes just covered by dozens of the adult WLS Moths when not many other big moths (or anything else for that matter) show up. Though a nuisance to me when I'm hoping to photograph rare beetles, they are important pollinators that fly by day as well as by night and therefore service a great variety of flowers.

The super speedy development of this multitude of caterpillars means that plant protein, abundant after the monsoon rains, is quickly turned into more palatable animal protein. It thus forms the basis of the food chain for many reptiles, birds and mammals. Even our Desert Tortoise, usually considered a vegetarian, cannot resist. Photo by Jan Emming

Or here, a coyote picking WLS caterpillars from a creosote bush (no idea why they had climbed it) photo by Gail Halm, an excellent observer of coyotes in the wild. She said 'he stood there for several minutes picking them off the bush'

Huge Hornworm

Huge, ready to pupate Rustic Sphinx Moth Caterpillar on oue Cape Honeysuckle today. I would not have seen it, if the pea-sized, hand-granade shaped droppings had not landed on the patio concrete. I'm adding the moth that I reared years ago from a cat like this. Maybe this is the great-great-......grand child of my moth. Manduca rustica Rustic sphinx, feeds on Desert Willow, Tacoma, Cape Honeysuckle, but never on Toamatoes, Peppers, Tobacco, Datura. Those hornworms are its cousins (Manduca sexta and M. quinquemaculata)

Clown or Hister Beetles

In the State Trust Land just beyond our property fence, several old saguaros are not looking healthy and big arms dropped to the ground. While these pieces first seemed to just shrink and mummify, recent rains brought forth a putrid stench of decay and decomposition. Time to look for insects that may use this resource. When I carefully lifted a piece yesterday, a shiny, flat beetle fell free. It's long protruding mandibles and square shape identified it as Hololepta, a Clown Beetle. Its hefty size, habitat and location speak for subgenus Leionota and species Hololepta yucateca

Hister beetles are found in all imaginable habitats with rich organic resources from beach debris to bird nests. Members of the nominate subgenus Hololepta are found under bark of decaying hardwoods; members of the subgenus Leionota in rotting vegetation incl. cactus, agave, and palms. Hister Beetle larvae and adults do not directly feed on the rotting material. Instead, they are predators, hunting other insects (such as maggots), and other small invertebrates.

Histeridae are among the larger beetle families. 440 spp. in 58 genera occur in our area (North America north of Mexico), ca. 4000 spp. in ~330 genera worldwide. At 20mm (2 of that are the prognath Mandibles) my smooth flatt black beetle is among the largest Histeridae I have seen.

Days after a Big Storm

After the wettest July on record, August is shaping up to really drown us. Two nights ago the regulatory washes that cut through our land were running over capacity several times, and sheet floods were reflecting the moonlight everywhere else. For hours, it sounded like freight trains racing by. Of course the dirt roads in Picture Rocks were impassable for hours. In the morning, the arroyo beds and our road were deeply scoured out. All the loose sand deposited by the last storm was gone, caliche and hard clay lie open. Our main wash that years ago was easy to walk across is now 5 to 6 feet deep with steeply eroded banks. The long roots of Ironwood trees, as thick as my upper arms, lay open and are badly abraded.

During the storm, wind gusts up to 60 mi/h and twisted branches off Palo Verdes and even Ironwood Trees. Several old Chollas and Prickly pears fell over. Some Barrel Cacti, just ready to bloom, also succumbed, following gravity’s pull when absorbed water made them top-heavy over roots anchored not very deeply in soggy soil.

But as destructive as the storms were, new life is now thriving all over the desert. Where there was bare sand for years, cheat grass and little yellow-blooming Asteraceae are covering the ground. Chamomile smell mixes with the aroma of wet, blooming creosote bushes and the heavy sweetness of Acacia flowers.

Barrel Cacti are crowned in wreaths of yellow, orange or deeper red flowers. Yellow stars sparkle on Pencil Chollas. Cactus Longhorns love juicy cacti for themselves and as hosts for their larvae. Sacred Datura and Devils Claw sprout from long dormant seeds and immediately get ready to produce new flowers. Mushrooms appear.

Long dead looking Desert Hackberry bushes leaf out and provide food for caterpillars - An Empress Leilia is hanging around, but I'm not sure if the caterpillars are hers. Even though most puddles from earlier storms seem to have evaporated much too quickly for any tadpole to develop, the ground is suddenly alive with hopping toadlets.

And while I'm taking these photos I'm providing nourishment, albeit involuntarily and under protest, to the next generation of Mosquitoes whose mothers also seemed to have appeared out of no-where

Monsoon Morning

A potent Thunderstorm woke us up today. There was no way out to go for a run: the road was a wash and all the washes were too deep to cross. 0 8 inches in half an hour and Tucson Mountain run-off will do that. Our Costa's Hummingbird was hiding under the eves, chirping indignantly, the Kestrel pair took to the blustery sky and would not stop screaming. I hope that does not mean that a big saguaro, containing their nest cavity, fell victim to the sudden onslaught of water. Why they would care about that in August I do not know. Curve-billed Thrashers were singing from the top of cacti. I did not get to go exploring any further: I found the garage had flooded and we needed to push the water out before it got into boxes of art work and materials stored there. Around 6 am the washes have already shrunk down to a trickle. Some spots of blue in the sky. But the next wall of clouds is moving in.