Invertebrates

Tarantulas are seen in the park during the day from time to time. Females can live for more than 20 years.

NPS Photo

Hundreds of species of insects, arachnids and other invertebrates find a home in the unique ecosystems of Montezuma Castle National Monument. These include harmless tarantulas as well as venomous black widow spiders and Arizona bark scorpions. However, these often misunderstoood desert inhabitants pose little threat to humans. The invertebrates found at Montezuma Castle and Montezuma Well reveal extraordinary evolutionary adaptations for survival in an arid desert environment.

 

Desert stink beetle

NPS Photo

Desert Stink Beetle (Eleodes spp.)

One of the most visible insects at Montezuma Castle, desert stink beetles are often seen along the trail. Not to be confused with true stinkbugs, they are also called pinacate beetles and are a type of darkling beetle. When threatened, they will raise their abdomen in the air and spray a smelly chemical at the threat. They are flightless and feed on decaying plant and animal material.

 

Adult tarantula

NPS Photo

Tarantula (Aphonopelma spp.)

Tarantulas are the largest spiders found in the continental US and some of the desert's most famous residents. Three species call the Verde Valley home. In spite of their intimidating appearance, tarantulas are calm and docile. Bites are very rare and their venom is not considered harmful to humans. Instead, tarantulas may flick bristles off of their abdomen at threats which can cause skin irritation.

They are most active during monsoon season from July through September which also coincides with their breeding season. They are most active at night, but are occasionally seen during the day. Tarantulas spend much of their time in silk-lined underground burrows either avoiding the heat of the day or waiting for prey to wander near their burrow. Tarantulas feed on lizards, insects, centipedes, and even mice.

 

Tarantula hawk with huntsman spider

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Tarantula Hawk (Pepsis spp.)

Tarantula hawks are large wasps named for their behavior of hunting tarantulas. Four species are found in the Verde Valley. All species are black with iridescent, bluish bodies, and most often have orange or brown wings. Females hunt tarantulas and other spiders and sting them to paralyze the spider. Once paralyzed, the wasp drags the spider to a burrow where she lays a single egg on the spider and covers the burrow. When the egg hatches, the larva slowly eats the spider alive before emerging from the burrow. Adult tarantula hawks are pollinators and feed on nectar.

Tarantula hawks are also famous for having one of the most painful stings of any insect in the world, though the pain only lasts about 15 minutes. However, like the tarantula, these intimidating wasps are not aggressive and will only sting if provoked.

 

Female velvet ant

Photo by Alejandro Santillana via Insects Unlocked

Velvet Ant (Dasymutilla spp.)

The females of this group of insects resemble large, fuzzy ants or flightless bumblebees, however they are actually wasps. Females do not have wings and can be seen scurrying along the ground. Many species have black and bright red or orange coloring to warn predators that they should be left alone; they possess a painful sting if handled. If threatened, they will also make a loud squeaking noise. The exoskeleton of these wasps is extremely tough. Adult velvet ants feed on nectar, while larvae usually feed on the larvae of other wasps or bees.

 

Red harvester ants

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Harvester Ants (Pogonomyrmex spp.)

Harvester ants collect seeds for their colonies and lines of them are often seen in the warm months bringing them back for storage. Their anthills are usually topped with fine gravel. If threatened, harvester ants will bite down and sting repeatedly. This signals to other ants that there is a threat nearby, similar to fire ants. Harvester ants only sting if provoked. Harvester ants make up about 90% of the diet of horned lizards. In the spring and summer, breeding swarms of flying ants can be encountered after a good rain. Often, many colonies swarm at the same time.

 

Fig beetle

Photo by Alan Schmierer

Fig Beetle (Cotinis mutabilis)

Also known as the figeater beetle or green fruit beetle, these large, colorful beetles are seen during the summer. They feed on cactus fruits and tree sap, but will also feed on soft cultivated fruit like figs, peaches, and tomatoes. They are closely related to June bugs and not especially graceful in flight, sometimes flying into unsuspecting visitors. Adults usually measure over one inch long (>3 cm).

 

Western black widow

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Western Black Widow (Latrodectus hesperus)

Perhaps the most recognizable spider in the world, black widows are common across the southwest and are most often found in darker, cooler areas such as woodpiles, cave entrances, as well as corners of buildings and roofs. Their webs are strong, sticky, and have an irregular structure and are most often used to trap ants, bees, and beetles. Males and young females can be mistaken for other species as females do not have the iconic red hourglass until they are older. Females of this species do not usually eat the male after breeding. Although females have a venomous bite, deaths are rare.

 

Arizona bark scorpion

Photo by rbelshee via CC0

Arizona Bark Scorpion (Centruroides sculpturatus)

The smallest species of scorpion found at Montezuma Castle is the Arizona bark scorpion, which can have a body length of up to three inches (8 cm). Because scorpions are nocturnal, visitors do not usually encounter them in the park. Bark scorpions have a habit of resting upside down on the underside of objects, which causes a number of people to be stung this way. They are the most venomous scorpion in North America and have a painful sting, but stings do not usually require medical treatment. Due to a compound in their exoskeleton, these scorpions, like many others, glow when viewed with ultraviolet light. Using black light is an easy way to observe scorpions at night.

Young scorpions (also known as scorplings) stay on their mother's back for protection after birth until their first molt. Scorpions are an important part of the desert food web and feed on cockroaches and other insects as well as spiders. They are also eaten by a variety of animals like owls and other birds, mice, tarantulas, snakes, javelinas, and pallid bats.

 

Crayfish

Photo by Alan Schmierer

Crayfish (Faxonius virilis)

Crayfish, also known as crawdads and crawfish, live in freshwater habitats such as streams, rivers, swamps, and ponds. There are over 500 species worldwide and about 150 species in North America. Crayfish are not native to Arizona. Originally released into reservoirs and large bodies of water as a food source for sport fish by people unaware of the devastating consequences, crayfish have invaded previously pristine waters negatively impacting native fish and aquatic ecosystems. This primarily nocturnal, armor-covered crustacean has few natural predators, is omnivorous, and competes for resources with fish, frogs, insects, and turtles. The crayfish propels itself backward through the water by using its tail composed of a central section called a telson and uropods on each side. It is able to walk on land and in the water by using its 4 pairs of walking legs. Each leg has an attached gill that occupies the bronchial chamber. The crayfish senses its world with its eyes, two pairs of antennae, and pincers called chelipeds. Crayfish have the ability to regenerate lost limbs. They molt as they grow, and often eat the old shell.