Venomous Pests: Inspectors Beware

by Nick Gromicko, CMI® and Kenton Shepard

Venomous pests are found virtually everywhere, and inspectors risk encountering one while visiting a property. For their safety, as well as the safety of their clients, inspectors should learn how to identify venomous insects and reptiles.
Bees and Wasps 
Bees and wasps are flying, stinging insects commonly found in and around homes throughout much of the world. Stings from these insects are normally not serious, except in people who are allergic to the venom or when large numbers of the insects attack at once. Even when they are not a serious threat, bees and wasps can be a nuisance and a source of fear, especially during the summer months when people gather outside the home. 
  • A few facts about bees and wasps:
    • More than half of all fruit and vegetable crops are pollinated by honey bees.
    • Wasps contribute to the ecological cycle by preying on many insect-pests that are harmful to crops.
  • Bees vs. Wasps: While many homeowners refer to bees and wasps interchangeably, inspectors should know the ways that they differ.  Differentiation between these insects is important because different methods may be necessary to remove them if they become a nuisance. Bees and wasps differ in the following ways:
    • Bees feed solely on pollen. Wasps, by contrast, are predatory and feed mostly on insects. Some common bees include honeybees, carpenter bees and bumblebees. Some common wasps are yellowjackets, hornets and paper wasps. Yellowjackets and hornets can appear virtually identical, although hornets usually have larger heads.
    • While bees have robust, hairy bodies with flat rear legs, wasps' bodies are slender with narrow waists connecting the thorax and abdomen. Wasps appear smooth and shiny and have slender legs shaped like cylinders.
    • Wasps, especially yellowjackets, are generally more aggressive than bees and they are more likely to come into contact with humans while in search of food. Wasps can become a nuisance in the warmer months because they often disrupt outdoor activities where meats and sweet liquids are present. A flying insect that repeatedly lands on a hot dog at a picnic or circles a dumpster is almost certainly not a bee.
    • Stinging wasps can sting repeatedly, while honeybees will die shortly after stinging once. Other bees, however, can sting repeatedly. 
  • Where do bees and wasps nest?
    • Bees and wasps prefer attics because they are warm and protected. They will find it easier to enter and infest an attic that is covered by slate or wood roofing as opposed to metal or asphalt shingles. Poor flashing may also allow easy insect entry. Inspectors entering attics with open (unscreened) gable vents should be on the lookout for bee or wasp infestation.
    • Yellowjackets typically nest underground using existing hollows. Occasionally, nests can be found in dark, enclosed areas in a building, such as crawlspaces, wall voids and attics. Nests are enclosed in a paper-like envelope, but they are rarely exposed or observed unless excavated. The nest entrance is small and inconspicuous. Colonies are readily defended because yellowjackets will sting when the nest area is disturbed.
    • Hornets produce large, conspicuous grayish paper-like nests in trees, shrubs and beneath building eaves.
    • Paper wasps will nest in small cavities in the sides of buildings, within metal gutters and poles, outdoor grills, and similar items.
    • Honeybees, unlike wasps and other types of bees, produce a persistent, perennial colony. These hives can grow very large, containing tens of thousands of bees, and are usually found outdoors, especially on trees. Hives that are discovered inside buildings must be eliminated as soon as possible. If allowed to develop, large amounts of wax and honey will be produced which may damage the building when the hive dies out or when the combs melt due to excessive heat. Rodents and insects will also be attracted to such sites.
    • Bumblebee nests are commonly constructed in abandoned rodent burrows, and they may also be found indoors in small hollow spaces, particularly if insulating debris is available.
  • Nest Control:  Nests should be destroyed if they are close enough to humans to pose a stinging threat. They should always be approached with caution, preferably at night when most of the "workers" are present but reluctant to fly. A few additional tips:  
    • Be aware that bees and wasps are attracted to lights, especially flashlights carried by inspectors as they enter dark attics or crawlspaces.
    • Use extreme caution when performing bee or wasp control from a ladder.
    • If a nest is not discovered until fall, control may be unnecessary, as imminent freezing temperatures will kill the colony. 
    • If there is direct access to the nest, a fast-acting dust or wettable powder formulation can be applied. If the nest must be removed during the daytime, a can of aerosol insect killer can be used to keep the bees or wasps at bay. Heavy clothing should be worn for added protection.
Rattlesnakes, copperheads, and other snakes often reside in crawlspaces with dirt floors and in a home’s landscaping and drainage. Snakes are easily startled and may react aggressively toward intruders. The following snakes may be encountered during inspections:
  • Bull snakes are large, non-venomous snakes common in the central parts of the U.S., northern Mexico and southern Canada. They are usually yellow in color, with brown, black or reddish- colored blotching. Due to its patterns and semi-keeled scalation, the bull snake is often mistaken for the Western Diamondback rattlesnake. The bull snake capitalizes on this similarity by performing an impressive rattlesnake impression when threatened; the snake can produce a convincing “rattle” sound, and flatten its head to appear more characteristically triangular. Their mimicry is so impressive that it is frequently the bull snake's undoing when discovered by humans.Copperhead snake. Notice the triangular head and vertically-oriented pupils, both characteristic of pit vipers. Also, the yellow-tipped tail indicates this is a juvenile
  • Copperheads are fairly large, venomous snakes with broad, triangular heads, vertically elliptical pupils, and heat-sensitive pits between each eye and nostril. The body is tan to brown, with dark "hourglass"-shaped crossbands down the length of the body. Small dark spots are common between crossbands on the back. The unpatterned head is dull orange, copper or rusty-red. When young, a copperhead has a yellow-tipped tail. The head is solid brown, and there are two tiny dots in the center of the top of the head. Copperheads are quite tolerant of habitat alteration and remain common in suburban areas of many large cities. They can be found throughout the eastern and central United States but are absent from most of Florida and south-central Georgia. Copperhead bites can be painful, although the symptoms are generally not as severe as bites from rattlesnakes.

  • Coral snakes possess the most potent venom of any North American snakes, and they can be found in a number of southern states from North Carolina to Texas, although they account for less than 1% of venomous snake bites in the U.S. There are several Coral snake and milk snake comparedreasons they don't claim more human victims -- they have short fangs that have difficulty penetrating clothing, they are more reclusive than most other snakes, and they typically inject only a relatively small quantity of venom when they bite. Any skin penetration, however, is a medical emergency that requires immediate attention. Coral snakes have a powerful neurotoxic venom that paralyzes the breathing muscles. The following symptoms are characteristic of coral snake envenomation:

    • nausea;
    • drowsiness;
    • vomiting;
    • excessive salivation;
    • difficulty breathing; and 
    • paralysis. 

  • It is important to note that coral snake bites do not result in significant swelling, discoloration or pain, and effects of the venom may take hours to develop.

    Identification: Physically, coral snakes are anomalies among North American venomous snakes. Unlike rattlesnakes, cottonmouths and copperheads, coral snakes are not pit vipers. Thus, they lack the characteristic pit viper's triangular head and vertically-oriented eyes, and they are quite small, shy and may appear harmless. Fortunately, they can be easily identified by their distinctive red, yellow and black color pattern. The sequence of these colors -- red-yellow-black -- is critical for identification, as other snakes perform a successful mimicry except in this one aspect. The harmless milk snake, for instance, would appear almost identical if its color pattern were not red-black-yellow. A useful way to remember this distinction is:  "Red touch yellow, kill a fellow. Red touch black, poison lack."Common, harmless garter snake

  • Garter snakes are harmless, and can be found everywhere from Canada to Central America. Most garter snakes are striped or banded lengthwise, and some are spotted between the stripes. They are found in moist environments, and most varieties are roughly 2 feet long.
  • Rattlesnakes are the most dangerous venomous snakes in North America. They bite thousands of people annually, although very few bites are fatal. The rattlesnake is easily distinguished by a rattle at the end of its tail, which is composed of a series of dried, hollow segments of skin which, when shaken, make a rattling sound. When the snake is alarmed, it shakes its tail, and the noise serves as a warning to the attacker. While most rattlesnakes are concentrated in the southwestern United States, they extend north, east and south in diminishing numbers and varieties. Every contiguous state has one or more varieties of rattlesnake. Rattlesnakes can be identified in the following ways:
    • broad, triangular head;
    • eyes have vertical "cat-like" pupils;
    • scales are keeled (raised center ridge);
    • body appears heavy or fat in the middle;
    • large tubular fangs that fold out when the mouth opens;
    • blunt tail with rattle, although baby rattlesnakes don't have Western Diamondback rattlesnake rattles, and some adult snakes may break or lose their rattles; and
    • typically, rattlesnakes range from 3 to 4 feet in length. Eastern Diamondback rattlesnakes can be significantly longer, however -- sometimes in excess of 7 feet.

      Symptoms of Rattlesnake Bites: 
  • pain and swelling in the area surrounding the bite (swelling may take several hours to develop);
    • rapid pulse and labored breathing;
    • progressive, general weakness;
    • visual impairment;
    • nausea and vomiting;
    • seizures; and
    • drowsiness or unconsciousness.

  • Differentiating Bull snakes from Rattlesnakes:
    The following tips can help prevent any confusion between these two snakes:
  • Bull snakes have no rattler. When threatened, they will often forcefully vibrate their tails which serves as a warning to potential predators. In dry leaves or grass, this will produce a sound that is quite similar to one emitted by a rattlesnake. Another related indicator is that bull snakes will keep their tails low to the ground while producing ther rattling sound, while most rattlesnakes will elevate their tail while rattling.
  • Although the two often have similar patterns, bull snakes are generally cream or pale yellow in color with brown or black markings; rattlesnakes, on the other hand, are typically much darker, depending upon the subspecies.
  • The body of a bull snake is more streamlined than that of a rattlesnake. A bull snake will be noticeably thinner and its body will become proportionately narrower down to its tail, Bull snake. Often mistaken for rattlesnakes, bull snakes are not as fat and lack the triangular head of a rattlerwhich ends at a defined point. A rattlesnake will appear thicker, particularly in its mid-section, with a more rounded tail due to its rattle.
  • The head of a bull snake is nearly identical in size to the upper portion of its body. The head of a rattlesnake, however, is more triangular in shape and is perceptibly wider than its upper body.
  • Bull snakes' pupils are circular, while those of rattlesnakes are vertically-oriented. All venomous snakes in North America have vertically-oriented pupils, except for the coral snake.
  • Bull snakes lay eggs, while rattlesnakes give birth to live offspring.
Most spiders pose no threat to humans. In fact, of the 20,000 species of spiders that inhabit the Americas, only 60 are capable of biting humans. Within that small group, only a handful of species are known to be dangerous to humans. Of these, only the brown recluse and the black widow have ever been associated with significant harm and rare reports of death. Tarantula bites, despite common fears, are not significantly more dangerous to humans than wasp stings.
  • Black widow spiders are perhaps the most venomous spiders in North America. 
    • Identification: The female black widow is normally shiny black, with a red "hourglass" marking on the underside of the abdomen. The abdominal marking may range in color from yellowish-orange to red, and its shape may range from an hourglass to a dot. In a few widow spiders, however, no pattern is obvious on the abdomen. The body of an adult black widow female is about 1/2-inch long, while the male widow spiders are smaller. They usually are not black in overall color, and instead appear light brown or gray and banded. Male widows may have an hourglass pattern, but coloration often is more orange and sometimes yellow. Widow spiders build loose and irregular mesh-type webs, often on plants, in loose stone and wood piles, and in the corners of rooms, garages and outbuildings. They do not produce the symmetrical web typical of orb-weaving spiders  or the distinctive "funnel" pattern of funnel weaver Black widow spider. Notice the red hourglass patternspiders.

    • Symptoms of Bite:  While the area around the bite may result in swelling, the venom is primarily a neurotoxin which does not cause significant localized tissue death. Rather, the venom, as well as other neurotoxins, affect the nervous system of the afflicted animal. Without medical attention, the symptoms of a black widow bite can last for days, and a complete recovery may take weeks. Black widow bites commonly cause the following symptoms:
      • painful rigidity in the muscles of the abdomen;
      • tightness in the chest accompanied by labored breathing;
      • elevated blood pressure;
      • elevated body temperature;
      • nausea; and
      • sweating.

Death is uncommon (less than 1% of the reported cases), but in the elderly or very young, death may occur from asphyxia. Seek medical attention if you suspect you have been bitten.

    • Habitat:  Black widow spiders and their relatives can be found almost anywhere in the Western hemisphere in damp and dark places. The spider prefers the following exterior environments:  woodpiles, rubble piles, under stones, in hollow stumps, and in rodent burrows, sheds and garages. Indoors, they are found in undisturbed, cluttered areas in basements and crawlspaces.

  • Brown Recluse:  Along with the black widow, the brown recluse is potentially the most dangerous spider in North America. Despite their reclusive habits, they do occasionally bite humans. Recluses typically bite when they are trapped between flesh and another surface, as when a sleeping human rolls over on a prowling spider, or when a person is putting on clothing or shoes containing the spider.Brown recluse spider

    • Identification:  The brown recluse is usually between 1/4-inch to 3/4-inch (6mm to 20mm) but may grow larger. They are notable for their characteristic "violin" pattern on the back of their cephalothorax -- the body part to which the legs attach. These spiders are not aggressive and bite only when threatened, usually when pressed up against the victim's skin. They seek out dark, warm, dry environments such as attics, closets, porches, barns, basements, woodpiles and old tires. 

    • Symptoms of Bite:
      • severe pain at bite site after about four hours;
      • severe itching;
      • nausea;
      • vomiting;
      • fever;
      • muscle pain; and
      • potentially severe localized tissue damage.

  • Hobo Spider:  This spider is not native to the U.S., but by the mid-1960s, it had become established in Washington, Oregon, Idaho and British Columbia. Current distribution places it also in Montana, northern Utah, and western Wyoming. Although the bite of the hobo spider is initially painless, it can be serious. Hobo spiders are often confused with wolf spiders, which produce a painful but relatively harmless bite. If serious symptoms develop, the victim should seek medical attention.

  • Symptoms of bite: Hobo Spider
    • immediate redness, which develops around the bite;
    • after 24 hours, the bite develops into a blister, and after 24 to 36 hours, the blister breaks open, leaving an open, oozing ulceration;
    • severe headache;
    • temporary memory loss;
    • impairment of vision;
    • nausea; and
    • weakness.

Preventing Spider Infestation

InterNACHI believes that spiders can be discouraged from entering the home by increasing lighting of darkened corners, such as by appropriate furniture arrangement and use of artificial lighting. Insecticides should be applied in dark, undisturbed areas where spiders are likely to produce webs. Insecticides also can be used to prevent spider migrations into homes by spraying around the exterior foundation and lower-story windows. Preventative spraying should be performed before temperatures get low since, by this point, spiders and other insects may have already entered the house. The insecticide chlorpyrifos (DursbanÒ) is the most widely available product for control of spiders around a home. Chlorpyrifos has a residual effectiveness of several weeks, particularly if not exposed to light and moisture. However, it is moderately toxic to humans.  
In summary, there are many kinds of venomous pests that inspectors may encounter in and around the homes they inspect, and knowing what they are and the hazards they pose can help inspectors act with appropriate caution.