Occasional Invaders

(Gryllus spp.)

Crickets are among the most common occasional invaders in Southern California — harmless individually, but a single cricket behind a wall or under an appliance at 2am is its own kind of problem. They’re drawn indoors by light and warmth as temperatures drop in late summer and fall, entering through gaps at doors, windows, and foundation voids. Once inside, they’ll feed on fabric, paper, and stored goods. Outdoors they congregate in mulch beds, ivy, and dense ground cover adjacent to the structure — the same conditions that sustain ant and earwig pressure. A perimeter treatment that addresses cricket harborage zones handles the problem before it gets through the door.

 (Halyomorpha halys)

An invasive species originally from East Asia, the brown marmorated stink bug arrived in the U.S. in the late 1990s and has steadily expanded its range across California. It’s a seasonal invader — as temperatures drop in fall, adults actively seek overwintering sites inside structures, entering through gaps around windows, doors, and utility penetrations. Once inside they go largely dormant, but warmth from heating systems can trigger activity mid-winter. The name earns its keep — when disturbed or crushed, the bug releases a distinctly unpleasant odor from glands on its abdomen. Outdoors it feeds on fruit trees, ornamentals, and vegetable gardens, making it a dual nuisance for homeowners with landscaped properties.

(Scutigera coleoptrata)

The house centipede is the one that makes people scream — 15 pairs of long banded legs, fast, and seemingly appearing from nowhere. Unlike most occasional invaders it doesn’t just pass through; it actively hunts inside structures, feeding on silverfish, cockroaches, spiders, and other small arthropods. Its presence indoors is often a signal that other pest pressure exists — centipedes follow the food supply. They’re moisture-dependent and enter through foundation gaps, drains, and utility penetrations, concentrating in bathrooms, basements, and crawl spaces where humidity is highest. The good news is they’re solitary and don’t establish colonies. The bad news is they’re fast enough that DIY control is more theatrical than effective. Addressing the moisture conditions and prey population that sustain them is the lasting fix — perimeter treatment handles the entry pressure.

 (Paravaejovis spinigerus — Stripe-Tailed Scorpion)

The scorpion is the occasional invader that gets the most attention — and in foothill communities across greater Los Angeles, it earns it. The stripe-tailed scorpion is the species most commonly encountered on Southern California properties — nocturnal, venomous, and capable of squeezing through gaps as narrow as a credit card. They enter structures through foundation cracks, weep screeds, and gaps around plumbing penetrations, concentrating in garages, attics, and ground-floor rooms. Their sting is painful but not medically significant for most healthy adults — the exception is the bark scorpion (Centruroides sculpturatus), occasionally documented in the eastern edges of Los Angeles County, whose venom requires medical attention. Scorpions are UV-fluorescent — a black light inspection is the most effective detection tool after dark. Exclusion, perimeter treatment, and reduction of harborage conditions around the foundation are the core control strategies.