Category: Wildfire

Living Jewels that Seek Fire and Eat Wood

Among the most important components that power the machinery of forest life are insects – beetles in particular play crucial ecological roles in forests.  One of the largest beetle families is the Buprestidae, represented by nearly 16,000 species. These creatures are known as “jewel beetles” due to their family’s spectacular array of iridescent colors and patterns. The insect pictured above is one dazzling example, native to the coniferous forests of the Rocky Mountains.

One of the world’s largest jewel beetles is Euchroma gigantea, native to Amazonia. These insects can measure over two inches in length. This is a mounted specimen from Brazil, part of the author’s collection.

In most living organisms, iridescence is enabled by pigmentation. Jewel beetles are different – their iridescence is structural in origin; microscopic texturing on the surfaces of their exoskeletons selectively reflects specific frequencies of light while absorbing others.

Most jewel beetles lay their eggs on dead or dying trees. Once the eggs hatch, the beetle larvae go to work, chewing their way through the wood. They leave a maze of tunnels in their wake. Some species of jewel beetles will lay their eggs only on freshly burned trees. These specialized insects are known as pyrophiles (literally, “fire loving”). Forest fires create a nearly instant Shagri-la for them.

The larvae (or grub) of a jewel beetle found inside a section of velvet mesquite wood. These larvae are often known as flathead borers due to the shape of their heads. The tunnels that such larvae create in dead wood are of great importance to forest ecology.

Pyrophilous jewel beetles have evolved specialized extra-large wing muscles to enable long distance flights to wildfire sites. These beetles have a way of finding burned trees that borders on the miraculous…

One of the buprestid beetles native to velvet mesquite bosques in southeastern Arizona. Note the heavyset, thickened body of this insect, a specialized morphology that allows room for large, powerful flight musculature.

When they fly, these beetles hold their bodies at an angle, in order to orient their underside to the direction of travel.  Minuscule texturing on the ventral side of the insect’s thorax functions mechanically in response to incredibly faint traces of infrared radiation (heat). Infrared radiation causes a pressure differential to occur in the thorax texturing. This fires neurons, sending a message to the beetle’s brain. The message says “fly in this direction and you will find a smorgasbord of freshly killed trees to provide food for your offspring.” What is even more amazing is that these insects can detect the heat given off by fires at distances up to fifty miles!  (research conducted by Dr. H.P. Bustami and associates at the University of Bonn [in Germany] brought this astounding facet of jewel beetle biology to light.)

A living jewel adorned with iridescent gold flecks and shimmering purple-sapphire elytra, this native buprestid inhabits local mesquite bosque habitats.

This relationship between forests, fire, and beetles has been going on for countless millennia. However, people often take a dim view of beetle larvae drilling tunnels in trees, claiming that this ruins otherwise “valuable” wood. Such anthropocentric views are myopic, for they exclude the needs of all other living things and turn a blind eye toward the ecology of forests. Jewel beetles benefit forests as agents of decomposition; the tunnels that their larvae bore in dead trees provide important open pathways for other insects and for the introduction of fungal spores. The tunnels facilitate the exchange of gasses in the wood and furnish the perfect moist, insulated, dark environ for fungi to take hold. Fungi are crucially important to living trees, to the health of the soil, and for their leading role in the recycling of nutrients via the decomposition of dead trees and other organic detritus. No forest on Earth can exist without fungi and decomposition.

This maze of tunnels was bored by jewel beetle grubs in a dead limb on a living velvet mesquite tree. Read the text above to discover why these tunnels are so beneficial to forest ecology.

This is a limb that was cut from the same tree as the one in the preceding image. However, this limb was cut when it was alive. Note the scarcity of holes and tunnels. Most jewel beetles lay their eggs only on dead wood, but there are a few exceptions to this rule.

Here in the desert southwest, jewel beetles are usually easy to find almost any place where trees are present. I have also found them rather often in upland desert habitats – areas that are essentially treeless. Buprestid beetles fly into these places seeking nectar and pollen meals from the wildflowers and flowering shrubs that grow there. Thus, they provide another important ecological function by acting as pollinators.

A Rare Bird Surprise, a Huge Insect, and the San Pedro River in October

It has been quite a while since I crafted a new post for this blog. During the past month, my life had been turned upside down with growing trepidation over the presidential election. I was not in a frame of mind conducive to writing. Now that the election is over, I feel a huge sense of relief and renewed hope. This was an election not only for the people, but one that will benefit wildlife and wild places as well.

I walked a perennial reach of the San Pedro River recently. There was  a new beaver dam, just a tiny one that was still under construction. Turkey, javelina, bobcat, deer, coyote, opossum, raccoon, and skunk tracks were visible in the mud along the stream’s edges. I was intrigued to find a set of feline tracks that suggested ocelot or jaguarundi, for they were certainly not made by a bobcat and were just as surely not left by a cougar, even a very young one.

A small, new beaver dam was discovered. This one was constructed using quite a few stones in addition to the usual combination of mud and tree branches.

October has finally brought some relief from the heat that so characterized this summer…109 consecutive, record-setting days of temperatures cresting at 100°F. or higher. The nights have cooled off and crisp air now graces our mornings. Our local woodlands have quieted considerably with the departure of many migratory birds, but there have been some amazing avian happenings here this month. A very rare event happened not long after the sun had set a few weeks ago. My wife, Kathleen, and I stepped outside to listen to the nocturnal sounds coming from the mesquite forest that surrounds our home. 

We heard it almost at once, a mysterious, alien-sounding voice emanating from midway up in the trees, only a few dozen yards distant. It was certainly an owl, but not a species that we had ever heard here before. On many a night, we have listened to the calls of great horned, western screech, barn, and elf owls in this woodland, but this was something new, something distinctly different. It suggested a screech owl, but both of us readily agreed that it was not “right.”

I had a growing hunch, so we went back indoors where we consulted a very useful website (xeno-canto.org), one that offers a multitude of audio files for most bird species across the globe. The first species that we chose to listen to was a bird whose range barely extends into the United States, a bird that inhabits oak and conifer habitats high on mountain slopes in extreme southeastern Arizona… 

As soon as we heard the recordings, we realized we had a whiskered screech owl hidden in the darkness of the tall mesquites only yards from our home! This was an owl that should not be here, for we live far from the high mountain slopes in the floor of a low-elevation valley. I believe that a major wildfire event from this past summer may provide the answer to this enigma. Less than 20 miles distant, the Bighorn Fire torched nearly all of the mid-to high elevation habitats off the face of an entire mountain range, the Santa Catalinas. Countless birds were driven off of those mountains, subsequently appearing in nearby places where they would ordinarily not be expected. For example, my friend Woody Hume, a very capable naturalist, told me that he had numbers of western bluebirds appearing at his place of residence not long after the fire. That is a species one does not expect to see during summer in the valley floor. Other such unusual species have been reported here this year. I would not be surprised if the owl that galvanized our attention had been living high in the Catalinas and wound up here, temporarily, as it looked for a new place to live.

A fully grown praying mantis crawls across my screen door. This is a gravid female, ready to lay her egg case, as evidenced by her swollen abdomen.

October and November brings new happenings in the insect world of southeastern Arizona. It is common to find adult preying mantises at this time of year. It is impressive to see one of these three-inch, bright green insects in flight. The individual pictured is an introduced species that has become widespread and firmly established in southern Arizona and other parts of our country.