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Pest Control Glossary — Chicago Terms and Definitions

Everything you need to know before hiring a pest control company.

Understanding pest control terminology helps you make better decisions when dealing with an infestation and hiring a professional. This glossary covers the most important terms used in the pest control industry — from treatment methods to pest biology to legal terms relevant to Chicago renters and landlords.

Treatment Methods

Heat Treatment
A chemical-free bed bug treatment that raises room or unit temperature to 120-135°F for several hours, killing all life stages including eggs in a single visit.
Chemical Treatment
Use of EPA-registered residual liquid insecticides applied to baseboards, harborage areas, and other targeted surfaces. Typically requires 2-3 visits to catch newly hatched insects.
Residual Treatment
Any insecticide application designed to remain active on a surface for weeks after application, killing pests that contact it during that window.
Fumigation
Use of a gaseous pesticide to penetrate an enclosed space and kill pests in inaccessible harborage. Rare in residential bed bug work; more common for structural pests like drywood termites in southern climates.
Integrated Pest Management (IPM)
A multi-tactic approach combining inspection, sanitation, exclusion, and targeted pesticide use rather than relying on a single method. The current professional standard.
Exclusion
Physically sealing the entry points pests use to enter a structure — steel mesh over gaps, sealants in cracks, door sweeps, vent covers. The only durable rodent solution.
Baiting
Use of attractant-based products that pests carry back to colonies, killing larger populations than contact sprays. Standard for ants and cockroaches.
Gel Bait
Highly attractive bait formulation applied in small dots in cracks, crevices, and behind appliances. The most effective product class for German cockroaches and many ant species.
Insect Growth Regulator (IGR)
A product that disrupts the molting and reproductive cycle of insects, sterilizing adults and preventing nymphs from reaching breeding age. Often combined with adulticide treatments.
Perimeter Treatment
Exterior insecticide application around a building's foundation to create a barrier against invading pests.
Barrier Treatment
General term for any treatment designed to prevent pests from crossing a boundary — exterior perimeter sprays, mosquito barrier treatments on landscaping, etc.
Spot Treatment
Targeted application limited to specific identified harborage or entry points rather than broadcast application across large areas.
Crack and Crevice Treatment
Precise insecticide application into structural gaps where pests harbor — baseboards, electrical outlets, plumbing penetrations. Standard for bed bug and cockroach work.

Pest Biology Terms

Harborage
Any location where pests hide, rest, and reproduce when not actively foraging. Identifying harborage is central to effective treatment.
Infestation
An established pest population in a structure with evidence of breeding — not just an occasional visitor.
Frass
Insect droppings. Cockroach frass looks like coarse ground pepper. Bed bug frass appears as small dark fecal staining on linens and harborage surfaces.
Nymph
An immature insect that resembles a smaller version of the adult. Bed bug nymphs pass through 5 molts before reaching adult size.
Molt / Shed Skin
The exoskeleton an insect sheds as it grows. Bed bug cast skins are translucent and bug-shaped and are a reliable sign of an active or recent infestation.
Egg Sac
A protective casing containing insect eggs. Cockroach egg sacs (oothecae) are visible brown cases. Spider egg sacs are silk packets.
Pheromone
A chemical signal insects use to communicate — aggregation pheromones bring bed bugs to a harborage, trail pheromones guide ants to food. Some professional products exploit pheromones to enhance bait attractiveness.
Vector
An organism that transmits disease. Some pests (mosquitoes, ticks, certain rodents) are public health vectors.
Harboring Site
Synonym for harborage — a specific identified location where pests are sheltering.
Colony
A social-insect population sharing one or more nests — applies to ants, wasps, hornets, bees, and termites.
Swarm
A reproductive flight of winged insects (ants, termites) leaving a parent colony to start new ones. Indoor swarms are a strong indicator of an established structural colony.
Life Cycle
The complete developmental sequence of an insect — egg, larval or nymph stages, adult. Effective treatment must address every stage present.

Inspection Terms

Visual Inspection
A trained technician's physical examination of harborage areas — mattress seams, baseboards, behind furniture, around appliances — looking for live insects, cast skins, fecal staining, and eggs.
Follow-Up Inspection
A visual re-inspection after treatment to confirm activity has stopped and verify that the warranty or guarantee period can begin.
Active Infestation
Confirmed presence of live, currently reproducing pests as opposed to evidence of a past, treated, or naturally died-off population.
Harboring Evidence
Physical signs that pests are sheltering at a specific location — droppings, cast skins, fecal staining, eggs, live insects.
Fecal Staining
Small dark dots or smears left by bed bug droppings on linens, mattress seams, and headboards. One of the most reliable visual indicators of an infestation.
Cast Skins
The exoskeletons bed bugs shed between life stages. Translucent, bug-shaped, and accumulate at harborage sites.
Interceptor (bed bug)
A passive monitoring device placed under bed and furniture legs that traps bed bugs crossing in or out. Useful for confirming presence and monitoring post-treatment clearance.
Monitor Station
Any device — interceptor, sticky trap, bait station with attractant — used to detect pest activity rather than to treat it.

Legal and Compliance Terms (Chicago)

RLTO (Residential Landlord Tenant Ordinance)
Chicago's primary tenant-rights law. Establishes habitability standards, including freedom from pest infestation, and lays out tenant remedies when a landlord fails to address pest issues.
Bed Bug Disclosure Law
Illinois law requires landlords to disclose any known bed bug infestation in a unit or building to prospective tenants. Failure to disclose carries civil penalties.
Habitability Standard
The legal requirement that a rental unit be fit for human occupation — including freedom from significant pest infestation. Violations support tenant remedies under Chicago's RLTO.
Notice to Treat
Formal written notification (typically required 48 hours in advance) that a landlord or pest control company will be entering a unit to perform pest treatment.
Re-entry Time
The amount of time residents must stay out of a treated area after application. Typically 30 minutes to 4 hours depending on product.
Service Report
Written documentation provided after every professional pest control visit listing pest, treatment method, products used, areas treated, and recommendations. Required by city inspectors and most property managers.
Certificate of Treatment
Formal documentation confirming a structure or unit was professionally treated. Often required by HOAs, employers, or city housing inspectors.
Illinois Department of Public Health
The state agency that licenses pest control companies and applicators in Illinois. License verification should be confirmed before hiring any pest control company.

Pest Types

Bed Bug
Small reddish-brown blood-feeding insects (Cimex lectularius) that hide in mattress seams, headboards, and structural cracks during the day and feed on sleeping humans at night.
German Cockroach
The most common indoor cockroach in Chicago. Small (1/2 inch), light brown, lives in warm humid spaces like kitchens and bathrooms. Reproduces rapidly and develops resistance to over-the-counter sprays.
American Cockroach
A large (1.5+ inch) reddish-brown cockroach more common in commercial spaces, sewers, basements, and lower floors of apartment buildings.
Norway Rat
The brown rat (Rattus norvegicus) — Chicago's primary rat species. Lives in burrows and sewers, climbs structures via utility lines, can squeeze through openings the size of a quarter.
House Mouse
Small gray-brown mouse (Mus musculus) that lives almost exclusively in human structures. Can squeeze through openings the size of a dime.
Carpenter Ant
Large black ants that excavate galleries in damp or damaged wood. Indicate moisture problems and can cause structural damage if left untreated.
Pavement Ant
Small dark ants that nest in soil under sidewalks, driveways, and slabs and forage indoors through baseboard gaps. One of the most common Chicago spring pests.
Yellow Jacket
Aggressive black-and-yellow ground-nesting wasp. Builds papery nests in soil, wall voids, and shed corners. Stings repeatedly.
Bald-Faced Hornet
Large black-and-white wasp that builds the football-shaped paper nests visible in trees and under eaves in late summer. Highly aggressive when defending the nest.
European Hornet
Large brown-and-yellow hornet, the only true hornet in North America. Less aggressive than bald-faced hornets but capable of significant stings.
Common House Spider
Small brown spider that builds tangled webs in corners, basements, and garages. Not medically significant.
Brown Recluse
Medically significant spider with a violin-shaped marking. Rare in Chicago but occasionally found in basements and stored items.
Wolf Spider
Large ground-dwelling spider that hunts rather than building webs. Common in basements and ground floors in fall. Painful but non-medically-significant bite.

Now that you know the terminology

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