Golden Paper Wasps

Paper wasps (genus Polistes) are the most common wasps of the Sonoran desert. They are about one inch long and often brightly colored (see photo gallery). According to the Arizona-Sonora Desert Museum, common paper wasps include the yellow (aka golden) paper wasp, the Navajo paper wasp, which is deep chocolate brown with the end of the abdomen yellowish; and the Arizona paper wasp, which is slightly smaller and more spindle-shaped than the other two and is brownish-red with thin yellow cross bands on the abdomen.

A golden paper wasp (Polistes aurifer) has been inspecting my house recently, but so far, I have not seen any nests. This wasp drinks from my pool. It can land on and walk on the water because it does not break surface tension. These wasps are not usually aggressive except when defending a nest. The nest is built using tree bark and wood fibers mixed with saliva.

ASDM: The paper wasp is a social insect whose life cycle begins as a solitary mated queen. The queen overwinters deep in rock cracks, behind peeling tar paper, or inside enclosures. In spring the queen builds a paper nest suspended from a thin stalk in a protected rock crevice, among thick vegetation such as dead fan palm leaves, or under the overhang of a man-made structure. She constructs a small cluster of paper hexagonal cells and lays an egg in each. The queen then feeds the larvae that hatch from these eggs a diet of caterpillar ‘meat balls.’ When the first young worker wasps emerge from their pupal cells, they assume the tasks of hunting caterpillars, collecting material for making papier-mâché for nest expansion, and collecting water for cooling. The queen then ceases all work except egg laying. By late spring, the colonies have grown to contain 20 to 50 wasps; by late summer as many as 200 wasps may be present. At this time new queens and males are reared. After mating, the new queens imbibe nectar to fatten for the winter. By late fall, the queen mother and workers die, the nest is abandoned, and the next generation of queens goes into hibernation.

Most wasps are specialized hunters that track down their prey using smell and sight combined with knowledge of the habitat, activity periods, and behavior of the prey. A solitary wasp usually subdues its prey with a sting that either kills the prey or paralyzes it briefly or permanently. (Tarantulas stung by tarantula hawks can live completely paralyzed for months.) Social wasps, including paper wasps, never sting their prey. Instead, they use their powerful cutting mandibles to chew the prey into pieces to feed directly to their larvae. The venom of social wasps is used only for defense. (Read more from ASDM)

Most wasps are carnivores that feed on other insects and arthropods. A few species have become herbivores, like bees, and feed on nectar and pollen.

Although wasps are not pleasant to have around, they are beneficial because they are pollinators.

See also: Tarantula Hawks Deliver The Big Sting  

A green lynx spider may be lurking in your yard

Spring flowers bring out the pollinators and their predators. I found one of those predators, a green lynx spider, lurking in the flower of a prickly pear cactus. Can you see the spider in the middle of the flower in the photo below?


 Rather than build a web to catch prey as some other spiders do, the green lynx spider lurks on foliage to catch prey. It pounces cat-like, hence its name “lynx.” Its color helps camouflage the spider. This is a fairly large spider; the body of a female can be nearly an inch long. The legs sport spiky hairs. This spider is big enough to tackle bees and butterflies.

As with most spiders, the green lynx spider paralyzes its prey with venom which also starts the digestion process. Spiders don’t have teeth, so the venom serves to liquify the prey so that the spider can suck up the juices.

In September and October, the female spider will build a silk sac and lay up to 600 eggs. She guards that sac and new hatchlings ferociously until after their first molt.

The green lynx spider is generally harmless to humans. So, if you have flowering prickly pear cactus in your yard, go out a take a close look in the flowers and on the pads. Maybe you will see a lurking “lynx.”

See more photos of the green lynx spider at the Arizona-Sonora Desert Museum digital library here.


Creatures of the Night: Bats

Big-brown-bat-Paul-BerquistBats have been around for at least 50 million years and in that time have evolved to take advantage of a great variety of habitats. The more than 1,000 species live on all continents except Antarctica and occur everywhere except in polar regions and in extreme deserts. They range from the very tiny, weighing less than a penny, to giants with wingspans over 6 feet.

Bats come in many colors: black, white, yellow, brown, orange, red, and blue-gray. Bats are mammals and have adapted almost every mammalian feeding strategy. Some are carnivores and hunt small rodents, birds, lizards, and frogs. Some are even fishermen. Some bats are herbivores and feed on plant nectar and fruit. Other bats are insectivores and play a large part in keeping insect numbers in check. And some bats are parasites; these are the vampires that survive by feeding on blood from other animals.  (The vampire bats don’t suck blood, they make a small incision and lap  up the blood.)

Lesser-Long-NoseBats are important pollinators for a variety of plants including the saguaro and other cacti. The fruit eaters help disperse the seeds.

Bats can fly, maneuver, and locate insects in complete darkness due to their acute hearing and practice of echolocation. Bats emit a sound, mostly in frequencies higher than human ears can detect. That sound bounces off objects and prey, and returns to the bat. The bats judge distant by the time delay of the returning sound.

Bats are not blind. Bat’s eyes contain rod photo-receptors for night vision and cone photo-receptors for daylight and color vision. They can see into the ultraviolet which helps them maneuver in twilight and better recognize UV-reflecting flowers during the day.

Bats live in crevices and caves, mines, under bridges, in attics or barns. Some bats hibernate, others migrate. I have a family of bats living somewhere near my house. At dusk on summer evenings, they come out and drink, on the fly, from my pool.

Bats, like other mammals, can carry rabies which is fatal to humans. The virus is transmitted by a bite. According to the CDC, it can also be transmitted when the saliva from a rabid animal comes in contact with a person’s mouth, eyes, nose, or a fresh wound. Some studies indicate that about 5% of the bat population carry rabies. Histoplasmosis, a fungus associated with bird and bat droppings, can become airborne and inhaled. Most infections are mild and produce either no symptoms or a minor influenza-like illness. On occasion, the disease can cause high fever, blood abnormalities, pneumonia and even death. The CDC says that “research suggests that bats might be the source of several hemorrhagic fevers, which affect multiple organ systems in the body and often lead to life-threatening diseases.” They also found bats carrying the deadly Marburg virus. Bats suspected of carrying these diseases live in Africa.

Bats, themselves, are subject to disease. Recently “white nose syndrome” has killed millions of bats mainly in the northeast U.S. This disease is suspected to be a fungus.

There are many places to observe bats around Tucson such as Saturday summer nights at the Arizona-Sonora Desert Museum. Other good places around Tucson include the East Broadway bridge over the Pantano Wash, the North Campbell Avenue bridge over the Rillito, and the East Tanque Verde bridge over the Rillito.

You can find photos and fact sheets on several bats of the Sonoran Desert here.

At Bat Conservation International you can find information on building bat houses and on how to safely and humanely remove a bat from your house.