As many people are already aware, moth and butterfly larvae are commonly referred to as caterpillars. While butterflies are among the few insect groups that are cherished by humans, moths have a well earned reputation as indoor pests that annoyingly fly around light sources. Humans are generally well disposed toward caterpillars despite the fact that a large number of species inflict painful and potentially dangerous stings to humans via their venomous spines. In Arizona, buckmoth caterpillars and several pus caterpillar species are common in backyards where they frequently sting residents and damage trees and valued plants. However, caterpillars are not considered house pests, except for one particular species that frequently establishes destructive infestations within homes located in southern Arizona. This species, Litoprosopus coachellae, often invades homes in large numbers where they tear apart carpeting, clothing, drapes and other valued fabrics in order to use the scraps for indoor cocoon construction.
In the US, L. coachellae caterpillars are only abundant in the southernmost areas of California and the southern half of Arizona, and they are commonly known as fan palm caterpillars due to their habit of establishing damaging infestations on palm trees. Indoor invasions often start after wind gusts push the caterpillars out of trees and onto residential lawns. From there, fan palm caterpillars enter homes due to their strong attraction to artificial light sources. Since the caterpillars may become injured upon ground impact, securing shelter indoors keeps the compromised insects safe from further weather disturbances and predators. One documented infestation case saw hundreds of the caterpillar pests crawl into a home after storm winds pushed the specimens onto the ground near a back door. However, recent research shows that fan palm caterpillars will often invade homes no matter the circumstances. Once indoors, fan palm caterpillars tear apart clothes, drapes, furniture upholstery and carpet in order to build a cocoon with the fibrous scraps. The damage these caterpillars inflict within homes can be costly, as they commonly render large patches of carpeting bald, and they destroy expensive fabrics, such as velvet, linen and wool.
Have you ever found an abundance of caterpillars in your home?