Monday, April 17, 2017

Easter walk at Saguaro National Park West

It was dry and hot and dusty. Of the wildflowers that the rainy (or here, not so rainy) winter had produced, only dry stalks and seed pods remained. Chollas and prickly pair were blooming, but I've seen better.

Insects were scarce. A bee fly with the ominous genus name Anthrax found the moisture and salt of my hand irresistible.

Foothills Palo Verdes, in beautiful bloom all over Picture Rocks, hardly showed any flowers here. But Ironwood trees were loaded with bursting buds.

There are few Mesquite Trees in the park and their flowers were past their prime. Still, they were the best source for beetles that I could find.

Megalostomis subfasciata

Coleothorpa axillaris
 Clytrin Leaf Beetles were flying around the fresh leaves, maybe searching spots to lay eggs.

Some mesquite catkins were covered in huge aggregations of mating Lycids. Often there are 2 species involved, but this time all I could find were Lucaina marginata , no L. discoidalis.

Lucaina marginata

They shared the catkins with many tiny Dermestid, Melyrid beetles and tiny Perdita Bees whose color is so close to that of the Mesquite flowers that it may take a second look to find them.

With its bee-like flight (the dark elytra stay folded over the body) Acmaeodera griffithi  could be overlooked by the beetle collector. Because I was trying to photograph solitary bees, I inadvertently focused on the Buprestid.

 While manipulating the Mesquite flowers to photograph the Perdita Bee, 2 tiny beetles landed on my hand. They are both  Dasytinae in the family Melyridae genus Trichochrous, the smaller one likely to be T. ferrugineus. (Thnks to Doug Yanega for getting this information from Adriean Mayor)

After only a quarter mile along the dusty road, our dogs were quite ready to go home to a drink and a bath in the tub. So this was a very short 'Osterspaziergang' but I could not completely let go of that lovely tradition.

Tuesday, April 11, 2017

As thick as thieves - a bee and a moth

The sky islands of Arizona are treasure islands for naturalists. When the desert wildflowers wilt in the per-summer heat of April and May, in these mountain ranges spring is only beginning. One of my favorite mountains is Mount Graham in eastern Arizona. On its highest elevations, it has beautiful mixed conifer areas and mountain meadows.

Mertensia macdougalii.
 in early summer, a herbaceousl plant in the family Borraginaceae covers acres of these meadows: Mertensia macdougalii. The flowers are set in swirls typical for this family. They are blue when fresh but change color to purple and pink when they age - probably due to ph changes in the aging flowers. They remind me very much of  Pulmonaria, an early spring herald of European forests.
Studying those flowers (looking for bugs on them) I soon noticed little injuries on the upper part most of the drooping flowers. The culprits were obvious too: bees were chewing through the side of the flower's throat to get to the nectar, instead of laboriously crawling into the flower. Easier on the bees, but of course this way, the flowers were probably left unpollinated. The bees that I observed were all of one species in the genus Colletes.

Colletes sp. bee chewing into the side of the flower to get to the nectar
Many Colletes are specialists, foraging for pollen on only one group of plants (Wilson and Messinger Carril). Even though my Mnt. Graham species is not identified and Mertensia is not mentioned in the bee-plant pairings of the book by Wilson and Merringer Carril, I may have stumbled on another such pair, or I just happened upon a group of bees (they are non-social but often nest in aggregations) that had found a good easy nectar source and stuck to it for the time being for reasons of efficiency (constancy principle).

middle: Colletes bee. right: damaged flower; left: moth
But I may have observed a clue that points to a long established relationship, which in this case is based on thievery: After trying to photograph the thieving bees for a while and thus establishing a search image for them, I realized that I was repeatedly looking not at a bee, but at a moth that was using the bee-created access to the nectar source.  Interstingly, the moth (Caloreas apocynoglossa) was always sitting head down while the bees would sit head-up. However, the moths' wing pattern 'took that into account': a dark hind-end  gave the impression of the dark head of the bee, even including antennae, and  a light patch imitated the  reflection on the bee's wings.

Moth Caloreas apocynoglossa
Two  interpretations are possible:
The bees may be armed with a painful sting - at least in comparison with a helpless moth. Predators would avoid bees and moths. So this would be direct Batesian mimicry.
But solitary bees are not usually heavily defended and many birds feed on them.

Another possibility is that the moth gains some protection from its head-down orientation: Flycatchers tend to grab their prey by head and thorax, in this case the pretend-bee-thorax - so the moth may be able to escape from the misdirected attack with minor hind-wing injuries (same idea as in hairstreaks).

But: If the relationship between bee and moth is old and established enough to have resulted in adaptive changes in behavior and pattern of the moth, it may be save to assume that the relationship of this Colletes species and Mertensia macdougalii is even older and that the bees are specialists. Too bad for the plant then, that these bees are specialized thieves!

Quoted: Thee Bees in your Backyard by JS Wilson, OM Carril, Priceton University Press 2016 

Thursday, March 16, 2017

Animals and their habitat: Harris Antelope Squirrel

 Cacti of the lower desert are important to the Harris Antelope Squirrels. They feed on the fruit of Barrel Cacti that are available all year round, ad generally stuff their big cheeks with anything from seeds to insects to even carrion. They are so dainty that they are able to jump into and hide in the most thorny Jumping Chollas. My dogs, and probably most hunting coyotes can only watch in deep frustration as the squirrel chitters only inches from their noses in relative safety. Besides coyotes, bobcats and hawks they have snakes to worry about. I have seen the little guys actively and aggressively take a stance against anything rattlesnake-related, even attacking and biting my snake stick that only smells of snakes. At this time (Feb. March) the squirrels raise their pups in underground (under cactus) burrows. All summer long, the day-active critters will brave the heat - one adaptation is their unusually high body temperature, also their little umbrella-tail and the habit of spread-eagling in shady places to dissipate heat to the cooler ground. During cold periods they seem to stay in their burrows, but during the last mild winter, a few were usually out and about.They are true denizens of the Sonoran Desert.

Animal Habitat: Cattleranch for Dung Beetles

Photo collage of my watercolor Longhorn Ranch and a digitally created inset of Canthon imitator rolling a dung ball.

Animals in their habitat: For some few animals human activity improved the environment. Cattle ranches must be paradise for many dung beetles, even in areas where historically no big grazing herds occurred. Of course it's not quite that simple:

Wednesday, March 15, 2017

Animals in their Habitat: Mountain Lion

Animals in their habitat: Mountain Lions in the Tucson Mountains. With the exception of humans, the mountain lion has the largest range of any large terrestrial mammal in the Western Hemisphere. They are found from Canada to Argentina. They are also able to utilize the low desert as well as the higher elevations of the Catalina Mountains and the territories of individuals are huge. Although they may snack on prey a...s small as mice, their main target in the Tucson Mountains are Javelinas and mostly Mule Deer. A female lion with two grown kittens pretty regularly shows up at a water feature in the backyard of a friend who lives around Gates Pass (SE Tucson Mountains). Sadly, one was killed on Picture Rocks Road some years ago - that's only a couple of miles from our house, but I've never seen tracks on our property. While I often see mountain lion footage of trail cameras at places where I do field work in AZ and Sonora Mexico, I've only seen one during the day in the wild. So the model for my painting was the female at the Phoenix Zoo - and if she was out here, she'd probably prefer a more seclude resting spot, maybe above my head in an old Mesquite Tree .. but hey, it's my painting ...

Tuesday, March 14, 2017

Animals in their habitat: Salt River Horses

Animals in their Habitat: Salt River Horses. This is a difficult topic. There is a community of horse lovers here who love this herd passionately and in a way defensively. Federal agencies have made weak attempts to remove them. When you observe the animals enjoying their free, rather secure live, splashing through the year-round running river, fighting for mates, forming bachelor groups and harems, raising foals, and all this trustingly in viewing distance of photographers and other admirers, you are apt to agree that they are a rare treasure.But any ecologist sees a growing herd of feral, not wild, horses that propagate unchecked by any meaningful predation in a very delicate desert environment. It seems difficult to find common ground. Even attempts to control birth-rates by chemical sterilization are vehemently decried by the human friends of the horses. The river so far is the saving grace - the members of the growing herd look well-fed and healthy and do not seem to stray too far into the real desert. I have not seen any impact studies concerning river banks or nitrate loads ...

Sunday, March 12, 2017

Animals and their habitat: Sphinx Moths and Sacred Datura

Watercolor and photo collage by M. Brummermann
The Moon Flower or Sacred Datura opens its flowers in the late evening. During the night, the main pollinators, Manduca spp. and other big Sphinx Moths, visit. In the morning there are still white-faced bees and other little insects crawling into the wilting flowers, but they are mostly too small to be effective pollinators.
The throat of Datura flowers is extraordinarily deep. When completely unrolled, the proboscis of Manduca rustica is long enough for the moth to hover over the flower and reach the nectar. Still, most moths land and crawl laboriously into the depth. They stay surprisingly long wiggling among anthers and stigma, and when they emerge, they head directly for another one of those white funnels. It is assumed that chemicals in the nectar may be slightly addictive and keep the moths faithful - thus assuring that precious pollen reaches its goal and does not get wasted. Datura (like many plants) is a known chemical powerhouse that produces potent Alkaloids. These may protect the plant tissue from many herbivores, but not from the caterpillars of several Manduca species who seem immune. So the pollinating moths can lay their eggs right on their favorite plant to produce a new generation for this symbiotic relationship.