Bug Blog

Monsoon Rains Will Trigger Insect And Arachnid Pest Activity In Urban And Suburban Areas

The arrival of the warm and rainy spring season gives rise to some of nature’s most beautiful products, such as blooming flowers, green foliage, rainbows, and unfortunately, massive numbers of insect and arachnid pests. In Arizona, it could be said that spring comes twice a year, once in March, and again in late July with the start of monsoon season. During the spring season in Arizona and elsewhere, increased daylight hours, higher humidity, warmer temperatures, and increased rainfall trigger both vegetation growth and  the emergence of insects that remain dormant during the winter. The arrival of monsoon season a few months later in July prompts a second wave of plant growth and insect activity in the Sonoran Desert.

In response to midsummer monsoon rains, ant and termite mating swarms emerge, grubs pupate into adult beetles, ocotillo plants sprout foliage, and agave plants bloom flowers. Surprisingly, entomologists, biologists, and many other groups of people travel to southern Arizona every year in late July solely to marvel at the diversity of plant and arthropod species that emerge in the region in response to monsoon rains. This annual gathering of professionals, laypeople, and amatuer scientists is known as the Invertebrates in Education and Conservation Conference, and it started back in 1990 as a way of celebrating Arizona’s diverse and unique arthropod fauna. The gathering sees vendors sell black widows, scorpions, ant queens, vinegaroons, sun spiders, numerous ant species, and tarantulas.

Observing insects and arachnids in the Sonoran Desert may be fun for a week out of the year while camping and hiking, but the midsummer proliferation of insects and arachnids in urban and suburban areas of Arizona is not so enjoyable for homeowners. In addition to increased termite and ant activity, a 5 inch fierce looking beetle species emerges in residential areas in massive numbers in response to monsoon rains. These beetles are known as Palo Verde root borers, and although they do not usually enter homes, they damage living trees, and their sizable presence in backyards makes them a tremendous nuisance. In fact, due to their abundance, Palo Verde root borers are the most “commonly seen species” in Tucson and Phoenix.

Other arthropod pests associated with monsoon season include crickets, Africanized honey bees, and red dog ticks. Monsoon rains flood ground burrows inhabited by tarantulas, prompting the arachnids to wander around human settings, and next month male tarantulas will be roaming the landscape in herds in an effort to find a mate. Monsoon season also sees scorpion-related incidents skyrocket in residential areas, so homeowners are strongly urged to avoid stepping into their yards barefoot.

Have you ever stepped on a venomous arthropod while barefoot?