You can find insects, spiders, and other multi-legged creatures (arthropods) anywhere in the world. So it is no surprise that there are thousands of species of arthropods in Joshua Tree National Park. They range in size from the four-inch-long tarantula (Aphonopelma iodium) and the green darner (Anax junius)-with its four-inch wingspread-to tiny gnats and mites. Joshua Tree's arthropods include the beautiful salmon-colored fairy shrimp (Branchinecta), the five-inch giant desert scorpion (Hadrurus arizonensis), and more than 75 species of butterflies. There are even more kinds of moths than butterflies. The yucca moth (Tegeticula paradoxa) is responsible for pollinating the Joshua trees after which the park is named.
All arthropods feature a hardened outer shell of exoskeleton, a segmented body, and jointed appendages. The activities of these small animals are most profoundly affected by their immediate environment: all the variations of temperature, moisture, space, and food that delimit their homes. These places are referred to as microhabitats. Some microhabitats are decidedly different from the surrounding environment. Take for example the soft-bodied, moisture-loving larva of the cactus fly (Copestylum mexicana) living in the very humid, warm environment of rotting cactus stems while surrounded by searing desert heat and single-digit relative humidity.
Several species of ants are found on the desert. Their varied adaptations are true wonders of nature. The harvester ants (Pogonomymex and Veromessor) busy themselves collecting seeds, which they store in underground granaries to use during the dry months. The honeypot ants (Myrmecocystus) have an exceptionally weird habit. Some members of the colony swallow so much honey that their abdomens get too large for them to move. They become, in effect, storage jars, providing food for the rest of the colony.
Giant Hairy Scorpion
Genus & SpeciesHadrurus hirsutus
Descriptionlength: 5.5 inches; color: pale yellow to olive brown. A waxy coating protects the scorpion from water loss.
Foodinsects, occasionally small lizards and snakes
Life HistoryYoung are born live and carried on the mother's back for 10-15 days before venturing out on their own.
Activitynocturnal and seldom encountered
Where to LookPinyon Well, Covington Flat, Pleasant Valley, Fried Liver Wash, Twin Tanks
NotesScorpions are preyed upon by owls and bats. Their sting has about the same effect as that of a wasp.
Genus & SpeciesAphonopelma iodium
DescriptionBody 2-3 inches; 4 inch legs; color is brown to black; covered with thousands of fine hairs. Besides its eight legs, the basic sections of a tarantula's body are its cephalothorax (a fused head and thorax, or chest) and its abdomen. It also has eight closely set eyes.
FoodInsects like beetles and grasshoppers, small lizards and mice. Tarantulas chase down their prey rather than snaring it in webs. Sensitive hairs on the spider's body allow it to detect subtle movements in its immediate environment and "home in" on a victim.
Life HistoryMates in fall; litter size is 500 to 1000. Females may live 20 years or more; males may be eaten during mating. Solitary, living one to a burrow.
HabitatJoshua tree forest; creosote scrub
ActivityWhen cornered by a predator, the tarantula will rub its hind legs over its abdomen, brushing hairs into its enemy's eyes.
Where to lookOasis of Mara, Split Rock, Wilson Canyon
NotesThese shy giants are reluctant to attack humans and their venom is no worse than a bee sting. More
Genus & SpeciesVanessa cardui
Descriptionupper side has tawny ground color, wing base is brown, oval white spot on forewing, black bar on forewing, hind wing has submarginal white spots; underwings have complex pattern; 2 to 2.5-inch wingspan
Foodthistles, mallow, yellow fiddleneck, sunflowers
Life Historymultiple broods; egg pale green, barrel-shaped; laid singly. Caterpillar varies from chartreuse with black marbling to purplish with yellow back stripe
Where to lookWilson Canyon, Jumbo Rocks, Indian Cove
NotesThe number of immigrants fluctuates greatly from one year to the next. Unlike the Monarch’s annual round-trip outings, the movements of the Painted Lady are essentially one-way.
Last updated: December 28, 2022