Big Bend Bugs
What’s the most common form of wildlife you’re likely to see in Big Bend National Park?
Insects make up more than half of all living things on Earth, comprising over one million species. They outnumber humans by 200 million to one: for every human, there are 200 million insects. This figure does not include non-insect arthropods, such as spiders and scorpions.
Observing insects, in the park or at home, will open up a whole new world of dimensions, color, form, activity, and beauty. You’ll find insects living in flowers, wood, earth, fabric, hair, blood, flesh, water, and dung. You’ll find them eating these same things, as well as grain, fungi, microbes, glue, spiders, and each other.
So where do you begin in your search to discover the insect world? Like most living things, insects are attracted to water, especially the still water of ponds. Sit quietly near a pond and watch for dragonflies and damselflies. These large, brightly-colored insects are voracious predators, and their legs form a “basket” that enables them to catch other insects in flight.
With its huge compound eyes, the dragonfly can detect prey up to 40 feet away. You might see clusters of small black beetles swimming and spinning at random around the water surface, resembling a group of bumper cars. These aptly-named whirligig beetles have two pairs of compound eyes; one pair looks for prey above the water surface, while the other pair looks for prey below the water. Beneath the surface, you might see water boatmen sculling through the water, powered by legs that are shaped like oars.
The arid desert also provides habitat for insects. Perhaps one of the most famous desert insects is the yucca moth. Observe a blooming yucca at night, and you may witness an example of insect pollination as these tiny white moths dart among the large white yucca flowers. The female yucca moth collects a ball of pollen from one or more yucca flowers. She deposits her eggs in the ovary of a flower, then puts the ball of pollen on the flower stigma, where it will fertilize the flower eggs. The moth larvae then feed on the developing seeds. A single yucca seedpod contains well over 100 seeds, and the moth larvae, which usually number only 1 or 2 per pod, eat relatively few seeds, sometimes fewer than a dozen each. While the yucca moth certainly benefits from this arrangement, the yucca itself also benefits, as most yuccas would remain un-pollinated and would not bear fruit if it were not for the pollination done by the moth.
Easier to witness is the pollinating activity of several types of bees found in the park. Most common are bumblebees, especially in beebrush plants in the Chisos Mountains. These large, heavy-bodied, fuzzy bees have black and yellow stripes on their abdomens. Although not native here, two types of honey bees are also found in Big Bend. European, or domestic, honey bees were brought to the United States from Europe several centuries ago and are now vital pollinators and honey producers; they provide 80% of the pollination required by agricultural crops in the United States, and one-third of our diet comes from crops pollinated by honey bees. These small bees appear virtually identical to their recently-immigrated cousins, the Africanized honey bees.
Only experts with powerful microscopes can distinguish the two types of honey bees. Behaviorally, though, these two honey bees are different. European honey bees are generally not very aggressive when threatened. Only a few bees defend the hive, and they not easily disturbed. When they are, they will usually only chase the attacker a short distance. Africanized honey bees, on the other hand, can be very aggressive. When they are threatened, many bees defend the hive. They are easily disturbed, especially by vibrations such as those from lawnmowers. Africanized honey bees will chase an attacker up to a quarter mile. We think of these as two distinct species of honey bees. However, they sometimes hybridize, producing crossbreeds with variable temperaments.
When entomologists analyze honey bees for identity, they study a number of anatomical characteristics and identify the degree of hybridization exhibited by a particular bee or colony of bees. For instance, a honey bee might be 25% European and 75% Africanized, or 50% Africanized and 50% European. Africanized honey bees have not attacked anyone in the park, but if bees chase you, you should:
Many hikers return from the summit of Emory Peak reporting hundreds, perhaps thousands, of ladybugs gathered on the peak, forming a bright red and black cover on every rock and tree trunk. These beetles appear to cluster at high elevations all over the southwestern United States for reasons that are not clearly understood. Many scientists believe that ladybugs fly to high elevations to escape temperature extremes; others believe that this gathering has to do with mating.
Spring and fall are good times to see monarch butterflies in Big Bend National Park. The park lies just west of one of the monarchs’ primary migration routes and receives many monarch visitors as they fly through here in April en route to summering grounds in the northern U.S. and Canada. In September they fly south to wintering grounds in central Mexico. These black and orange butterflies travel over 1,000 miles on their migratory journey, covering up to 80 miles per day. No one monarch makes the entire round-trip migration; since they stop to breed along the way, the butterflies that we see flying north in the spring may be five generations removed from those that originally migrated south in the fall. Monarchs are only one of many species of moths and butterflies that inhabit the park. Look for red admirals, mourning cloaks, sisters, dog-faced sulphurs, and various types of swallowtails; brilliantly colored tiger swallowtails stand out the most, but the duller pipevine swallowtails are more common. At night look for the black witch moth, one of the largest moths in North America.
In the late spring and early summer, people often see tarantula hawks flying low over the ground, searching for tarantulas. These large black wasps with golden wings, also known as pepsis wasps, will sting people if annoyed but seldom do, so intent are they upon finding arachnid prey. The female tarantula hawk stings the spider only to paralyze it, but not kill it. She drags the inert body into her tunnel, lays her eggs on it, and then seals the tunnel shut with pebbles and dirt. The wasp larvae hatch and eat the tarantula’s body for a week or two. If the female wasp had killed the tarantula instead of paralyzing it, it would decay before the larvae could eat all of it. When the larvae finish eating the spider, they are old enough to move onto their next developmental phase.
While there are many types of grasshoppers in the park, two types are most commonly seen. The desert lubber grasshopper is large, chunky, and sports a vivid black and yellow body; when it flies, it flashes bright red wings. The smaller red-winged grasshopper is slim and black-bodied and may be hard to see at rest, as it hides in vegetation. Its large, bright red wings clearly stand out when it flies. With active curiosity and careful observation you will see many more types of insects during your visit to Big Bend National Park. An amazing display of beauty and diversity surrounds us, if we are willing to put aside our prejudices and explore the lives of the insects around us.
Did You Know?
The predominant shrub found in Big Bend National Park is creosote. While most shrubs lose their leaves in winter, creosote maintains its resinous foliage year round. After a rainstorm, the shrubs "green-up" and produce small, yellow flowers several times a year. More...