Pest Library

Why does putting a name to it change the building work?

Because the name is shorthand for a behavior, and the behavior is the thing you end up repairing.

Two black ants can cross the same kitchen counter on the same August afternoon. One of them came from a colony sitting in a section of band joist that a failed gutter has held above fifteen percent moisture content for three seasons, and it is enlarging a void inside a load path. The other walked in from under the front walk through an expansion joint and will lose interest when the weather turns. Both are ants. Both die under the same aerosol. Only one of them means somebody should be pulling trim off to look at framing.

Penn State’s extension entomologists put a number on the first case that is worth carrying around: carpenter ants will not infest wood that is sound and below fifteen percent moisture. That single figure converts an insect into a plumbing and drainage question. It also explains why a treatment that kills every ant on the property can be followed by an identical problem two springs later — nothing that was done addressed the reason the site qualified.

The same logic runs through all twenty profiles collected here. A mouse and a rat are not a size difference, they are two different sealing specifications. A German cockroach and an Oriental cockroach are not two shades of brown, they are an interior harborage problem and an exterior moisture problem respectively, and they are solved in different places by different trades. A yellowjacket in a wall and a bald-faced hornet on a branch look like one job to a homeowner and are two entirely separate operations with different risks.

So the library is not a catalog of things that are unpleasant. It is a set of building diagnoses filed under the animal that gives them away. Arnold Katz, who founded this company in 1983, took his degree in entomology at the University of Georgia, and the habit of starting from the organism and reasoning outward to the structure is the part of that training which survived into how the work is done now. Each profile ends where a service page begins, and the pest control overview explains how those services fit together.

What four questions separate twenty pests?

Ask these before you ask what it is called, because they sort the whole library into four piles and the piles determine the work.

Is it consuming the structure? Very few things are. In this region the list is essentially eastern subterranean termites, carpenter ants and carpenter bees, and only the first of the three actually eats wood — the other two remove it to live in it. Everything else in this library is doing something to your building, not to your framing. Getting this question right early is what stops a homeowner treating a nuisance as a structural emergency and, far worse, the reverse.

Is it breeding indoors or arriving from outdoors? This is the question that decides whether sealing helps at all. German cockroaches, bed bugs and pharaoh ants complete their entire life cycle inside heated structures and do not maintain outdoor populations here; sealing the exterior does nothing for any of them, and the work is interior harborage, sanitation and slow bait pressure. Cluster flies, Oriental cockroaches, paper wasps and mice are outdoor organisms exploiting your building; for those, the envelope is the whole argument.

Is it living here or passing through? A carpenter bee gallery in a fascia board is a residence. A foraging pavement ant on a counter may have traveled from a nest under the driveway. Frass, droppings, staining, nest material and repeated activity in the same spot indicate residence. Occasional sightings that move around the house usually indicate foraging, and the nest is somewhere you have not looked.

Does it carry a legal or health constraint that changes the timing? Three groups do. Bats are protected and a colony cannot simply be removed on demand. Raccoons and bats are both rabies vector species in New York according to the State Department of Health, which changes who touches the animal and what happens afterwards. And nuisance wildlife removal in New York is regulated by the Department of Environmental Conservation, which requires a permit for some species and specifies how animals taken outside of season are handled. None of that applies to an insect, and all of it applies before a ladder goes up.

Answer those four and you have usually narrowed twenty candidates to three. The sections below take it the rest of the way.

Which ant do you have, and is it a structural problem or a nuisance?

Four ants in this library hang off ant control, and exactly one of them is a wood problem.

The carpenter ant is the large one, variable in size from roughly a quarter inch to three quarters of an inch, with an evenly rounded thorax in profile and a single node at the waist. What it pushes out of a gallery is the diagnostic feature, not the ant: a coarse, fibrous debris containing shredded wood and the discarded body parts of insects, sifting from a crack and collecting on the sill below. Termite galleries by contrast hold soil and fecal pellets. If you are finding that material under a window head, a porch beam or a bath wall, the colony is above it and there is water behind it.

The odorous house ant is the small dark one that smells sharply when crushed, about an eighth of an inch, workers uniform in size, with the waist node hidden from above. Its significance is not damage; it is that a colony frequently occupies several connected nests at once. That is why an aerosol at the trail so often converts one problem into three, and why the work starts with mapping the trail back rather than interrupting it.

The pavement ant is slightly larger, dull rather than glossy because of fine grooves on the head and thorax, with two nodes at the waist. It nests under slabs, walkways, patios and steps and comes up through expansion joints, slab-to-foundation gaps and the perimeter of a finished basement floor. It is a genuine nuisance and it is almost never a sign that anything is wrong with your structure, which is a useful thing to be told plainly.

The pharaoh ant is the smallest of the four at about a sixteenth of an inch, pale yellow to reddish, easily dismissed as a speck. It matters far more than its size suggests. It cannot survive a New York winter outdoors, it lives permanently inside heated buildings, it maintains many queens, and it responds to a repellent spray by splitting and relocating. In a hospital, a care setting or a large residential building, spraying a pharaoh ant trail is how a contained problem becomes a building-wide one. Cornell’s guidance is blunt about the general principle: correct identification is what makes the management plan, and with this species the identification is the whole plan.

Mouse or rat: what actually changes between the two?

The gap you have to close, the material you close it with, and where the work happens.

The house mouse and the Norway rat both sit under rodent control, and rodent exclusion is the core of what this company does, but they are not the same job. Cornell’s exclusion guidance separates them by mesh: quarter-inch hardware cloth is the appropriate size for mice and bats, while half-inch is the coarser option. That is not a detail, it is the specification. A screened vent that stops rats will pass mice indefinitely, and a building sealed to rat standard can still have a mouse population with no visible sign of failure anywhere.

Distinguishing them by evidence is straightforward once you know what to look at. Cornell’s rodent material puts daily dropping output at roughly forty to fifty for a rat and fifty to sixty for a mouse, so sheer quantity settles nothing — but size, shape and distribution tell you a great deal. Mouse droppings are small and pointed; rat droppings are markedly larger and blunt. Mice scatter droppings along a route as they travel and feed in many small sites; rats concentrate them near harborage and runs. Cornell also flags sebum marks, the oily brown deposit that accumulates on surfaces rodents use repeatedly, and mixed dropping sizes as an indicator that both adults and juveniles are present, which is the difference between an incursion and an established population.

Then the structural half. A mouse problem is usually a problem of the building envelope above grade: sill plate junctions, utility penetrations, garage door corners, dryer vent flappers, soffit returns and the gap behind a corroded foundation vent screen. A Norway rat problem is usually a problem below grade or at the ground plane: burrows against a foundation, a broken house trap or cellar drain line, a sidewalk vault, a cellar door that no longer seats, a gap under a stoop. In a New York City building, rats frequently arrive from underneath rather than from the perimeter, which is why sealing the front of the building achieves nothing.

Whatever the species, the closure material is what determines whether the work holds. Cornell’s own list names galvanised sheet metal as durable and resistant to removal when it is screwed rather than pushed into place, and stainless mesh as stronger still. Expanding foam is the most common closure in this industry and the most common failure in it; rodents chew straight through it and the repair looks finished from three feet away. What we fit instead is sheet metal fabricated to the opening on site, mortar and cement where the substrate is masonry, and Xcluder fabric and sweeps at doors, backed by mesh and screwed fixings rather than adhesive. The whole method is set out under structural exclusion.

Which cockroach is it, and what does the species tell you about the building?

Three species, three completely different diagnoses, and the identification takes about four seconds once you know the marks.

The German cockroach is the small one, half to five-eighths of an inch, tan to brown with two parallel dark bands running front to back on the shield behind the head. It is the only one of the three that will not persist outdoors in this climate, which means every German cockroach in your building arrived inside something and is breeding in the kitchen, the bathroom or the void behind them. Cornell’s guidance explains why bait rather than spray is the center of the work: transferring the active ingredient from foraging insects back to hidden females is one of the few routes to the part of the population you never see. Cornell also records the reason this species matters in housing rather than merely being unwelcome: allergenic proteins in cockroach droppings are a documented trigger and sustainer of asthma in both children and adults. In a multi-unit building the pathways are plumbing chases and shared risers, which is why unit-by-unit work fails and building-level work does not.

The American cockroach is the very large one, one to just over one and a half inches, reddish brown, and it is the insect most New Yorkers mean when they say water bug. Finding one in an apartment is rarely a hygiene finding. It is usually a plumbing finding: a dry floor drain trap, a broken house trap, an open cleanout, a chase running down to a cellar that connects to the sewer. Treating the apartment treats the symptom of a connection that exists three floors below it.

The Oriental cockroach is dark brown to black, three quarters to just over an inch, and it wants cold and damp rather than warmth. It lives in cellars, crawlspaces, window wells, leaf litter and drains, and it moves indoors when its outdoor situation deteriorates. It is the one species of the three where perimeter and drainage work is genuinely the main event: leaders discharging against the foundation, a window well without a cover, a crawlspace with a soil floor and no vapor barrier. All three profiles sit under cockroach control.

Wasp, hornet or bee: why does nest position matter more than species?

Because where the nest is decides the risk and the method, and the species mostly tells you what to expect when you get there.

The eastern yellowjacket is the one that ends up inside a structure. Cornell records that some yellowjacket species nest in trees, others in structures, and others in rodent burrows and compost or leaf piles — meaning a wall void, a soffit box or an abandoned burrow under a step are all normal choices. Eastern yellowjacket colonies reach roughly two to three thousand workers by the end of summer. The rule that follows is absolute: an active colony’s entrance is never plugged, because the workers then chew a new route and the new route frequently opens on the inside of the wall.

The bald-faced hornet builds the gray papier-mâché football everybody recognizes, with colonies growing to something like eight hundred workers. It is visible, which makes it easier to plan and more dangerous to approach casually. Position governs everything: a nest in a tree twenty feet from the house is a different decision from a nest tucked under a soffit return where the envelope is already open.

The paper wasp builds the small open comb without an envelope, hung under an eave or an overhang that keeps rain off it, and its colonies run to a few dozen individuals rather than thousands. Cornell notes that paper wasps often warn an intruder by flying into them without stinging, where yellowjackets are the more aggressive counterpart and release alarm pheromone when crushed. The European paper wasp, now the commonest paper wasp in the Northeast, is the frequent misidentification — long legs, tapered abdomen, orange-tipped antennae, and yellowjacket coloring.

The carpenter bee is the outlier in the group. It is not a colony insect and it is not primarily a sting problem; it is a wood problem, drilling a clean round entrance into unpainted or weathered softwood and then turning to run a gallery with the grain. Fascia, rake boards, deck rails, pergolas and porch ceilings are the usual targets, and the woodpecker damage that follows is often worse than the original tunnel. All four sit under wasp and hornet removal.

What is above the ceiling, and what does New York law allow you to do about it?

Identify the animal first, then check what the state permits, and only then get on a ladder. This is the one group in the library where the sequence is legally rather than practically constrained.

The eastern gray squirrel is diurnal, so the tell is timing: running and scratching that starts around first light and again in the late afternoon, from the ceiling below the roof rather than deeper in the house. Entry is at the roofline — a rotted soffit return, a gable louver with failed screening, a ridge vent lifted at one end, the corner where a lower roof meets a wall. NYSDEC’s guidance is that gray, black and fox squirrels require a permit when the animal is a nuisance, though action may be taken without one where it is damaging property.

The raccoon announces itself by weight. The movement is heavier, slower, after dark, and often accompanied by vocalisation from young in spring. Raccoons open buildings rather than slipping into them: they will pull a soffit panel, work a roof vent free, or use an uncapped chimney as a den. NYSDEC treats them the same way — a permit for nuisance situations, action allowed where there is property damage, and animals taken outside the open season must be buried or cremated immediately. They are also a rabies vector species in this state, which is the reason handling is not a homeowner activity.

The big brown bat is the most constrained of the three and the most often mishandled. NYSDEC directs New Yorkers to contact a DEC wildlife office or a licensed nuisance wildlife control operator when bats are involved, on the grounds that some species are protected and identification requires an expert. The Department of Health’s position on bats found inside occupied space is separate and concerns rabies exposure and testing. Practically, the work is a one-way exclusion device fitted after the emergence route has been established by watching the building at dusk, followed by sealing every other opening — and it cannot be done at a time when flightless young would be sealed inside. Trapping is not the method, and neither is a spray.

All three profiles sit under wildlife management, and in each case the removal step is the short part and the licensed part — it is coordinated with nuisance wildlife partner firms rather than done in-house. The sealing that follows is what decides whether the same hole is used again next year, and it is the reason these three animals belong on a pest library run by an exclusion company.

Which four pests define a service on their own?

Four of the twenty are singular enough that the pest and the service are effectively the same subject.

The bed bug is an obligate blood feeder that spreads by being carried, not by flying or by dirt. Cornell is direct on the health question: bed bugs feed exclusively on blood and are not known to transmit disease to people, though the welts can become infected from scratching. That fact matters because the panic frequently exceeds the medical stake while the building stake is badly underestimated. In an apartment building the insect moves through shared walls, conduit runs and the voids around plumbing penetrations, so a single treated unit surrounded by unassessed neighbors is a bill rather than an outcome. The work is on bed bug treatment.

The eastern subterranean termite is the only insect in this library that eats structural wood as food. Cornell describes the mud tubes as narrow strings of dried mud built as sheltering runways on foundation walls, allowing workers to move between the below-ground nest and the food source while staying enclosed and damp. Swarms occur in spring, roughly February through May, and a swarm indoors is the single clearest diagnostic event a homeowner is likely to get. Cornell’s prevention advice is structural rather than chemical: reduce moisture near wood, keep non-wood borders between soil and timber, keep the soil dry near the foundation, and keep lumber and wood debris away from the building. It is also the one profile in this library with no service page behind it, because termite treatment is not work Graduate carries out. The entry earns its place on identification instead: the question that comes first is nearly always whether the insect is a termite or a carpenter ant, and the two answers lead to entirely different places.

The Asian tiger mosquito is a container breeder and a daytime biter, and it is the reason a fogging schedule can run all summer while the biting continues. Cornell records that this species needs only a quarter inch of water to complete its life cycle, and that the common house mosquito generally stays within three hundred feet of where it emerged. Put those two facts together and the conclusion is uncomfortable but useful: if you are being bitten in your own yard, the water producing them is almost certainly in your own yard. Plant saucers, clogged gutters, corrugated leader extensions, tarps, bins, boat covers and forgotten buckets do it. See mosquito management for how the property survey works.

The cluster fly is the one people find hardest to believe. Its larvae are parasites of earthworms in soil, so the insect has nothing to do with refuse, food or hygiene. Adults move to sunlit walls in autumn and work their way into wall voids, attics and unheated rooms to overwinter, then appear in numbers indoors during warm winter spells. Penn State’s extension service advises against treating inside a structure after the flies are already in, and notes that insecticidal dust in a void can attract carpet beetles to feed on the accumulated dead insects — a second problem created by the treatment for the first. Sealing is the answer here, and that is why the profile is filed under structural exclusion instead of under a treatment service.

What does the calendar tell you before anyone identifies anything?

Timing narrows the list before you have looked at a single insect, and in a couple of cases it settles the identification outright.

Late winter into spring belongs to swarming. Cornell puts eastern subterranean termite swarms between February and May, and winged carpenter ants often show up indoors at roughly the same time. The two get confused constantly, and the separation is easy once you know the three marks Penn State sets out: ants have elbowed antennae, termites have straight, bead-like ones; ants have a pinched waist, termites do not; and an ant’s front wing is longer than its hind wing, while a termite’s four wings are about equal.

Late spring and early summer is nest founding. Cornell notes that yellowjacket and hornet colonies are started by overwintering mated queens and run from May through September in the Northeast. A nest that can be dealt with quickly in June is an eight-hundred-worker or three-thousand-worker proposition by late August, which is the practical case for not waiting.

High summer is mosquito production and carpenter bee gallery extension, and it is also when carpenter ant foraging is most visible. Penn State notes that carpenter ant workers forage at night, with peak activity between about ten in the evening and two in the morning, which is why a homeowner who only looks during the day may see nothing while a colony is fully active.

Autumn is the most important window in the year and the one most often missed. It is when mice, cluster flies, Oriental cockroaches and overwintering paper wasps all move toward structures at once, for the same reason. A building closed in September never acquires that population. The same building closed in January has to have an interior population dealt with first, which is longer and more disruptive work. If there is one piece of scheduling advice in this whole library, it is that one.

Winter is diagnostic. On a genuinely cold day, the places where warm air escapes a building are the places pests use to get into it, because they are the same openings. Bats, in contrast, run on a protected calendar of their own, and that calendar governs when exclusion can proceed regardless of what is convenient.

Does the same species behave differently in a city building than in a house?

Yes, and in several cases the species is effectively a different problem in the two settings.

In a detached Long Island house, most of the twenty are perimeter problems. There is a single envelope with one owner, a foundation, a roofline and a yard, and the fault list repeats from house to house: the sill plate line, corroded vent screens, a crawlspace hatch that has dropped out of square, bulkhead edges, penetrations sleeved but left open, the bottom corners of an overhead garage door, and the gaps where a roof plane dies into a wall. The soil contact and the yard also bring in the pests the city largely does not have to think about. Termites need soil, carpenter bees need exposed weathered trim, cluster flies need earthworm-rich lawn soil nearby, and Asian tiger mosquitoes need containers holding water. Older North Shore stock adds another layer: rubble and fieldstone walls whose joints lose mortar every winter, opening entry for rodents and for Oriental cockroaches at the same time. The regional picture is on the Long Island page.

In a New York City building the important routes are internal and vertical. Plumbing chases, shared risers, conduit runs and the voids at joist pockets in party walls connect units to each other far more effectively than the front door connects them to the street. That is why German cockroaches, bed bugs and pharaoh ants — the three species in this library that live permanently indoors — are disproportionately city problems, and why treating one apartment reduces the count in that apartment while redistributing the remainder. Add compactor rooms, refuse chutes, sidewalk hatches, cellar doors and sidewalk vaults and you have a set of rat pathways that no individual resident is in a position to close. The city picture is on the New York City page, and the building-level version of the argument, including what boards and managing agents are actually obliged to do, is on the commercial hub.

The consequence is the same in both settings but it lands differently. On Long Island, the person who has the problem can usually authorise the fix. In the city, they frequently cannot, and knowing that early saves a year of treating a symptom.

What should you do, and not do, before an identification is confirmed?

A short list, because the wrong first move is expensive and several of them are instinctive.

Collect the specimen if you safely can. A dead insect in a small clear container or a piece of tape is worth ten descriptions, and it survives the trip in a way a memory does not. Photograph the evidence in place as well as the animal, and put something of known size in the frame — a coin, a key, a ruler. Scale is the most common casualty of a phone photograph, and it is precisely what separates a young rat from an adult mouse.

Note where and when. Which room, which wall, what height, what time of day, and whether it was one or many. For anything you hear rather than see, the time of day is close to diagnostic on its own.

Leave the frass, the droppings and the staining where they are until someone has looked at them. Cleaning up is a reasonable instinct and it removes the map. If it has to be cleaned for health reasons, photograph it first.

Do not spray a trail of small ants. Several of the species here respond to a repellent by scattering and establishing new nests, so the visible result is fewer ants for a week and more nests thereafter. Do not plug the entrance of an active wasp or hornet colony in a wall. Do not treat a cluster fly wall void from inside. Do not seal a building that still has an active rodent population inside it, because the sealing then traps them in the wall cavities rather than excluding them. And do not attempt to remove a bat, a raccoon or a squirrel yourself; the legal position, the rabies question and the possibility of dependent young are all reasons that decision belongs elsewhere.

Finally, be honest about bites. Skin reactions are the least reliable evidence in this entire library. People react very differently to the same insect, and a confident conclusion drawn from marks alone has sent a great many households down the wrong path for months. Physical evidence decides it.

How should you use these twenty profiles?

Start from the group that matches your evidence, read the one profile that fits, then follow it to the service page it hangs off.

Ants: carpenter ant, odorous house ant, pavement ant and pharaoh ant. Rodents: house mouse and Norway rat. Cockroaches: German, American and Oriental. Stinging insects and wood bees: eastern yellowjacket, bald-faced hornet, paper wasp and carpenter bee. Wildlife: eastern gray squirrel, raccoon and big brown bat. And the four that stand alone: bed bug, eastern subterranean termite, Asian tiger mosquito and cluster fly.

If the profile you land on describes your situation, the service page underneath it describes the work. If two profiles both seem to fit, that is normal and it is usually resolved by one piece of physical evidence rather than by more reading.

If you would rather describe what you have found to a person than key it out yourself, get in touch with the building’s age, the room, the evidence and the time of day you noticed it. That is generally enough to narrow it before anyone drives anywhere. For the person behind the work and how he approaches it, read Ryan Katz’s page. And if the outcome you actually want is a building that stops producing the problem at all, read structural exclusion first — for most of the twenty animals in this library, that is where the durable half of the answer lives.

Reading the signs