Sunday, August 29, 2010

Visit to an Enchanted Canyon

Sunday, Aug. 29, 2010
We started up Pima Canyon very early this morning to get the first stretch of open desert at the southern flank of the Santa Catalina Mountains behind us before it got too hot. When we descended into the canyon we found it brimming with live and very much changed from my June visit.

Every little meadow was covered in flowers. Unlike in spring, when golden poppies color the hillsides, more muted whites, purples and blues were now the dominant hues.

Several species of Morning Glories bloomed in clear blues, purples and even bright scarlet.

Wait-a-minute Acacias reached over the path. Succulent vines weighed down mesquite trees.

Deep orange Gulf Fritillaries betrayed the presence of their caterpillars on a wild Passiflora vine .

Golden-headed Scallopwings (Staphylus ceos) and Arizona Powdered Skippers (Systasea zampa) basked in sunny spots.

Slant-faced Montezuma's (Syrbula montezuma), Toothpick (Paropomala sp.) and Two-striped Mermiria Grasshoppers (Mermiria bivittata) jumped in the grassy areas and filled the air with their constant chirping.

White-lined Birdgrasshoppers (Schistocerca albolineata) and Panther-spotted Grasshoppers (Poecilotettix pantherinus) were clinging to shrubbery.

The trail was a flightpath to Giant Swallowtails and White-spotted Purples and a transit route to Harvester Ants. I tucked my pant legs into my socks one sting too late. A huge Two-tailed Swallowtail tried to land on the delicate morning Glories.

Larvae of the strangest-looking tortoise beetle, Physonota arizonae, were skeletonizing the leaves of Canyon Ragweed while holding a protective umbrella of excrement over their backs.

By eleven o'clock it became quite muggy in the narrow canyon under the thick canopy of Mesquite trees and Cottonwoods. A refreshing wind sprang up and made me find an unobstructed view of the sky: white billowing clouds were rolling over the ridge of the Catalinas from the north east. We weren't quite ready to retreat: the ascent had been too strenuous and we had come too far to give up already.

It was worth it: Just beyond the next bend of the trail I found a orange-glowing spot bobbing up and down under the bushes.

It moved like a Clear-wing but its wings were opaque. I could barely see this because their rapid beat never slowed down.

Only the stop-motion effect of the camera flash made it possible to see the details. The heavy body was banded like a hornet's.

Something flashed brilliant-blue like a peacock's tail: surprisingly, the hind legs legs were heavily 'feathered' and dragged like a train. An Anchiornis of moths!

It turned out that I was watching an ovipositing Glorious Squash Vine Borer, Melittia gloriosa.
She was laying her eggs into the dead leaves under a Wait-a-minute Acacia and some dead-looking vines. I had not seen any Squash Vines during our canyon hike. Melittia gloriosa is the largest and most colorful of the melon (Cucurbita) borers found in the western United States. The larvae are known to attack the large fleshy cucurbit tubers found underground.

While I was fascinated and distracted by the moth, the first drops of rain rattled the bushes above. As I hastily made my way down the canyon it got ominously dark. At least it wasn't hot anymore. Still, the fast pace and the load of camera and water bottles had me drenched in sweat very soon. Lightning struck the north side of the canyon and thunder crackled right after it. A biting chemical smell hung in the air.

Looking back over my shoulder up Pima Canyon

Luckily the storm wasn't moving with me along the canyon, and the clouds above broke before I had to go down the last exposed part of the trail.

Thursday, August 26, 2010

A 'Young Beetle', Complete Metamorphosis

Seven-spot and Convergent Lady Beetle, both adult

"Is he getting any bigger than this?" "Is this a young Lady Bug?" These are questions that I hear very often. The answer is of course that adult beetles do not grow, and the lady bugs are two different species.

Yucca Plantbugs Halticotoma valida, adult and nymphs

I also often hear the description that "Big beetles were surrounded by their little ones". In this case the omni-present term 'Bug' would have been a better fit, because this person had most likely seen a group of True Bugs. Bugs do indeed often care for their off-spring, and those kids do resemble their parents. True Bugs undergo an incomplete metamorphosis as described in an earlier blog chapter. Visit also Ashley Wood's photo stream who followed the life cycle of many European bug species in beautifully detailed drawings
Larval stages of a Stink Bug by A. Wood

Young beetles, however, bear no similarity to their parents. Insects that have the full, hard wing covers that identify them as beetles, are adults and do not grow. If they are small, and some are barely a millimeter long, they stay that way, and make the life of a beetle photographer very difficult. Beetles, like butterflies, flies, and bees and wasps, undergo a complete metamorphosis.

Ashy-gray Lady Beetle, Olla-v nigra, adults and larva

Like all insects, beetles lay eggs. They are usually deposited on or close to the food that the hatching larvae will eat and that's all the care most beetle off-spring will receive. After hatching, beetle larvae feed voraciously. Growing and storing energy is their only purpose in life. Most are not very invested in locomotion, their legs are short and their bodies are huge. Well developed mouth-parts deliver food to the intestinal system that seems to take up most of the segmented, elongated body.
Beetle larvae live in almost all biological niches imaginable. Some live as predators in leaf-litter, under tree bark, and in fresh water, and even on flowers.

Predators, of course, move well and have well developed sensory organs to find their prey.

Larvae of Dermestes marmoratus on cow carcass

Many beetle larvae are invaluable for the decomposition of dead animals, feces, and dead plant material.

Pattern left by Bark Beetle females and their larvae, outer bark removed

Some live protected in the nests of other insect species as brood parasites, devouring provisions and off-spring alike. Others live off living plant parts, boring or mining inside wood, fruits or leaves

Leaf beetle larvae: cryptic (left), aposematic (middle), actively disgusting holding excrement package (right)

The ones that are chewing away openly on the outside are usually protected by cryptic, mimetic or aposematic colors, shapes, and or behaviors. Some even build their own protective cases.

Scarab grub

Cellulose feeders like many scarab larvae tend to be especially big: they not only eat very bulky food, they also house a whole world of cellulose digesting symbiotic organisms in their guts.

Beetle larvae may be storage pests and raid organic material horded by squirrels, pack-rats, and humans. This includes starchy products as well as fur coats and insect collections. But as far as I know, no beetle species, larvae or adults, directly parasitises any living warm-blooded animal.

Examples of Erotylidae larvae (left) and Curculionidae (right) by A. Zaitsev

In adaptation to the demands of so many different environments and ways of life, beetle larvae come in many very different shapes. Artem Zaitsev's exceptional work, shown on his flickr photostream, gives you an impression of the multitude of morphological adaptations.

Endocrinological control of larval development:

To grow, beetle larvae have to molt out of their rigid chitinous skin to a 'larger size'. This happens several times until finally the larvae changes into the stiff, immobile pupa from which eventually the adult beetle emerges.
Delicate shifts in the balance of three hormones determine whether a molt leads from one larval stage to just another, larger one, or to pupation and thus metamorphosis.
In short, Prothoracicotropic Hormone (PTTH) is released from the brain and activates the prothoracic glands to release Ecdysone. Two endocrine glands (corpora allata) in the head of the larva are producing Juvenile Hormone (JH). An increase in Ecdysone while the JH levels in the heamolymph of the larva are high will cause molting into another, larger larva. An increase in Ecdysone when the levels of JH are low will cause the larva to molt and undergo pupation and metamorphosis instead. PTTH release and corpora allata activty (JH production) are controlled by the central nervous system that is able to integrate endogen and exogen inputs (body size, age, food availability, day length etc.)

The beetle pupa is not as tightly enclosed as a Butterfly chrysalis. Appendices like legs, antennae or wings are already clearly recognizable. But the pupa is covered by a dense chitinous layer that protects against dehydration. While the pupa rests without moving or feeding, radical changes take place inside, the metamorphosis. Tissues are actually dissolved to be reshaped into completely different organs. Compound eyes, chemically sensitive antennae, wings and sexual organs develop while the feeding apparatus is reduced. At the end of the pupal rest the sexually mature adult beetle will hatch (eclose) from the pupal skin.

Mating Soldier Beetles, Chauliognathus profundus

The adult beetles do not grow. Many species don't eat at all or just replenish their resources with easily digested sugars. Their only purpose is now the propagation of the species. Most are able to fly and are thus highly mobile. This allows them to disperse and find unrelated mating partners for a healthy exchange of gens and possibly fresh unexploited living-space for their off-spring. Since most adults either don't eat, or have a different diet from the larvae, there is no competition for resources among the generations.

Adults and larvae of Altica ambiens completely defoliate small alders

The advantage of this arrangement is easy to understand after observing one of the exemptions: Alder Flea Beetle (Altica ambiens) larvae and adults both eat the leaves of Alders and often totally denude the little trees. I'm not quite sure how the next generation survives. Maybe there is some built-in prolonged pause in the sequence of generations that allows the trees to recover.

But back to our 'Young Beetle':
On a Mount Lemmon trip of the Sabino Canyon Naturalists led by Ned Harris, we actually found what could really be called a 'young beetle'. It was Mid-August an it had been raining. Even the mountain climate was humid and warm enough to be called muggy. The area along the Oracle Ridge trail was heavily burnt several years ago. The dead trees are still upright and soot and carbonized parts have been eroded away. These are ideal conditions for many different fungi and the mushroom connoisseur among beetles, Gibbifer californicus, the Pleasing Fungus Beetle.

First we found some adults and last instar larvae, and then a whole gallery of hanging pupae. About 60 of them were lined up under the protective overhang of a leaning tree. Some where already empty.
Perched on top of pupae and empty cases was a ghostly white beetle with his under-wings partly unfolded.
This very freshly eclosed Fungus beetle showed nothing yet of the characteristic blue coloration or any of the black accents. This was a teneral specimen, a true young beetle. His final colors became apparent only hours later when his new exoskeleton had completely dried.

The mature color of Gibbifer californicus ranges from gray to deep blue (left) and purple. However, the beautiful color does not survive the death of the beetle. Gibbifer californicus specimen in collections are of a sickly yellow hue, only the black extremities remain dark.
Incidentally, the illustration in the Peterson Field guide (right) depicts a beetle with those non-colors to represent the species. That image was one of the triggers that started my collection of life-images of Arizona beetle species.

Saturday, August 21, 2010

Nothing is what it seems at Willcox Playa

August 8, 2010.Charlie O'Brien and I arrived at Willcox Playa around ten thirty and the temperature was already climbing into the upper nineties. On the flat salt pan, there is not much shade. The white sand reflects the sun and seems to double its intensity. Looking for bugs, we spent a lot of time close to the radiantly hot ground. Cooling off in the air-conditioned car between stops kept us going.

A dirt road parallels the tracks of the Union Pacific Railroad. We followed along with a shipment of huge windmill blades going to California. Far ahead, water was rushing. Across the road? We could see it churning and spilling down from the higher eastern embankment. Charlie and I couldn't quite agree where it was coming from. It seemed to be spouting out of a huge pipeline. But the closer we got, the smaller the stream of water became. Finally, there was no water crossing the road at all. All we found was a muddy pool of standing water on the west side of the road. Everything else, a mirage.

Those temporary pools of murky rainwater were full of life. Little pulsating openings turned out to be the mouths of big golden tadpoles, floating up-side-down while skimming debris off the surface and probably gulping air into their developing lungs. Just when my brain had formed the search image 'tadpole' I realized that some of the creatures had oddly segmented tails. Tadpole Shrimp (Triops sp.)! Dormant eggs had been hidden in the dry sand since the last flood maybe a year or two ago. The recent rains made them hatch and the little crustaceans developed within days in warm standing water. They have to race through their whole life cycle and produce new eggs before the temporary desert ponds dry out again. They have done this in nearly unchanged form for the last 70 million years and are considered the oldest animal species on earth. I had read about these predatory living fossils, but I had no idea that they would be so big (about 3 cm).

Metallic green insects, nearly invisible in the glare of sun on white sand, were running and flying like wasps or flies along the water's edge. I didn't fall for that deception: Tiger Beetles were my main interest on this trip.We caught 4 species but we saw many more. They had the wind on their side: it kept blowing any that flew up out of reach across the water. Some additional species came to the black light at night at Twin Lakes. We'll have to return for the other 70 or so species.

The rains had also triggered many wild flower seeds to sprout. The dominant plant, a purple-blooming nightshade, seemed to be already covered in reddish berries (most likely poisonous). Or were they Lady Bugs? They turned out to be the larvae of Ten-lined Potato Beetles, Leptinotarsa decemlineata. I assume that they can advertise their presence with their contrasting colors because they are as indigestible to predators as their alkaloid-loaded host plant. Their similarity to bad tasting Lady Bugs may enhance the protection (Müllerian mimicry)

At closer inspection, some of the narrow, silvery buds of the nightshade turned out to be beetles that fit exactly in color, shape and even venation: Epicauta tricostata (above and below, left). These are blister beetles, with chemical defenses of their own and probably rather safe, even if their cover is blown.
But some of the beetles were just harmless imitators: False Blister Beetles, Oedemeridae (above, right). The silvery white color of both beetle species is of course not just cryptic or deceptive: like the surface of the silvery leaves of the nightshades, it serves as sun protection.

Something was running on the ground between the wide-spaced grasses. It looked nearly like a fairly big spider and certainly acted like one. So at first I hesitated to reach for it, just long enough to let it get away. Then, of course, we caught it in a container. It turned out to be another Meloid, Negalius mamoratus (all Meloid ids by John Pinto). This one was dark, but an air cushion under slightly inflated elytra seemed to efficiently protect it from overheating by radiation.

There is a narrow range of optimal temperatures for any ectotherm, active organisms. We noticed later that these beetles climb up into higher grasses to sleep as soon as it gets to cool to keep the running-spider illusion going.

At Twin Lakes, a bare, round sandy spot of several feet diameter with an off-center entrance hole seemed to indicate a Harvester Ant nest. After some painful experiences, I approach those only carefully. But I always check around them for Anteater Scarabs, genus Chremastocheilus. So far without luck, so that will be another story. This time the entrance hole, while in the right location of the arena, was quite small and very round. Only a single hymenopteran was working, a harvester-ant-mimicking Ammophila wasp (A. formicoides or A. wrightii. thanks, Eric Eaton for the id options). She slipped inside, grabbed an 'armful' of sand, moved all the way to the outside of the flat area to drop her load on an inconspicuous slope, and immediately returned for more. She kept using the same dump site and her times inside the hole kept getting longer and longer as she dug deeper. Eventually she'll catch and paralyze a caterpillar, drag it into her hole, lay an egg on it and seal the chamber. Her larva will develop inside the living, paralyzed host until she pupates and then hatches as another winged huntress.

We moved on to the dunes of Blue Sky Road. By now it was afternoon and a thunderstorm over the Chiricahuas sent chilling blasts of wind into the Playa and the sun dissapeared behind clouds. All around the dayactive insects were retiring. A beetle in the genus Rhipiphoris nearly had me believe that he was a wasp - with his long clear wings, reduced elytra, imitation of a hymenopteran waist, and huge shiny eyes, and the way he was clinging to a dry stick just like a sleepy wasp in the evening .

A small fuzzy Clerid, Enoclerus analis (ID Jaques Rifkind), hanging on a blade of dry grass, and a dusk active Carabid, Panagaeus relative Micrixys distincta (Haldeman), running on the ground, gave both convincing imitations of female velvet ants that are famous for their painful sting.

On a Cholla Cactus several weevils of the species Gerstaeckeria unicolor were clinging to the tufts of glochids where they were nearly invisible, except to a weevil expert like Charlie who knows exactly where to look.

A round, moving dot in the sand could have been a tumbling seed or maybe a spider, but the little hairy Tenebrionid Edrotes arens did not at all look like a beetle.

Finally Charlie scared up a very pretty Checkered Garter Snake, Thamnophis marcianus. These shy reptiles usually just glide away as fast as possible. Instead, this one tried to intimidate us by taking the defensive stance of a rattler.

Mimicry, warning colors, cryptic shapes and behaviors, camouflage colors and patterns, and protective behaviors are used by animals of all habitats. Just check out the page from an old German Lexicon. But at Willcox Playa, deception seems to be the rule. There, due to a complete lack of cover, everyone has to hide in plain sight.