Part 3

STINGING ARTHROPODS

1. ANTS (Order: Hymenoptera; Family: Formicidae)

Identification. Like other Hymenoptera, females of dangerous ant species have a stinger at the posterior tip of the abdomen. Their constricted “waist” between the thorax and posterior abdomen and their elbowed antennae distinguish them from similar insects. The dangerous United States species belong to genera Solenopsis (fire ants) or Pogonomyrmex (harvester ants). The easiest way to distinguish these ants is by their mounds. Fire ants build elevated earthen mounds 8-90 cm (3-36 in) high, leaving the surrounding vegetation relatively undisturbed. In contrast, harvester ant mounds are usually flat or slightly elevated and are surrounded by a defoliated area 0.6-3 m (2-10 ft) or more in diameter. Also, harvester ants are 2 to 3 times larger than fire ants.

Distribution. The Florida harvester ant, P. badius, distributed throughout the Southeastern States, is the only harvester ant known to occur east of the Mississippi River. West of the Mississippi, the red harvester ant (P. barbatus), the California harvester ant (P. californicus), and the western harvester ant (P. occidentalis) are found in different individualized distribution areas. The two most important fire ant species were introduced into the United States from South America. The red imported fire ant (S. invicta) was introduced about 1940 and is well established in the Southeastern States. Currently, this ant infests Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North and South Carolina, and Texas. The black imported fire ant (S. richteri) was introduced about 1918; its distribution is limited to an area in northeastern Mississippi and northwestern Alabama. Two less important native species, S. geminata (tropical or native fire ant) and S. xyloni (southern fire ant), occur in localized areas of a few southern states.

Biology/Behavior. Ants of the Solenopsis and Pogonomyrmex genera are diurnal soil-inhabiting insects that prefer to nest in open areas. These ants are social insects; their colonies consist of at least one reproductive queen, several males, and many nonreproductive female workers. Fire and harvester ants are particularly dangerous because workers defending their nest can inflict repeated stings, and multiple human envenomizations may occur when a victim comes in contact with a mound.

Avoidance/Control. Familiarization with the appearance of the ant mounds is necessary in order to avoid them and prevent accidental envenomizations. Since small children are often the victims of multiple stings, parents should insure that the mounds of dangerous ant species are not present in play areas. This is particularly important where the red imported fire ant occurs. Mound treatments with mirex have been effective in controlling Solenopsis and Pogonomyrmex ants. The Environmental Protection Agency limits the use of this insecticide, and it must be applied in strict accordance with EPA and product label instructions.

Envenomization Reaction/Treatment. (See appendix.)

2. BEES (Order: Hymenoptera; Family: Apidae)

Identification. Two families of bees are commonly associated with human envenomization: Apidae (honey bees and bumble bees) and Halictidae (sweat bees). Only the honey bees and bumble bees are considered dangerous. Both are robust hairy insects with two pairs of membranous wings which they hold at an angular position over the body when at rest. Microscopic examination shows that bee thoracic hairs are individually “feathered.” In contrast, wasp thoracic hairs are smooth.

Distribution. Dangerous species of bees are distributed throughout the United States.

Biology/Behavior. 1. Honey Bees. Since these insects are not native to this continent, north of Mexico, all original honey bee colonies in the United States were imported. Apis mellifera, the cosmopolitan bee of commerce, is responsible for most bee stings and many deaths. This species is separated into several races, with the gold Italian and the black or gray Caucasian races making up the majority of the bees found in this country. The aggressive Brazilian (hybrid African) bee is currently restricted to the South American continent. Honey bees are highly social insects. Their colony consists of an egg-laying queen, drones to fertilize the queen, and workers to gather food and care for the young. Honey bees can release “alarm odors” associated with the sting gland, which cause other bees in the vicinity of an odor-marked victim to attack and inflict multiple stings. Unlike other hymenopterous insects, the honey bee worker has a barbed stinger and can sting only once; to escape, the bee must leave its entire stinging apparatus attached to the skin of its victim. As important pollinators of crops, honey bees are very beneficial to man.

2. Bumble Bees. The bumble bees are considered to be the most primitive of the social bees. Their colonies lack much of the structure and highly evolved behavior of the honey bees; however, like the honey bees, the bumble bees are diurnal plant feeders and important pollinators of crops. A typical colony consists of at least one queen, several males, and numerous workers. Only young fertilized queens survive the winter to establish new colonies the next spring. The nests are normally located deep in undisturbed ground, like fence rows, and are supplied with a mixture of pollen and honey. During late summer, a colony usually contains between 100 and 500 bees. Although bumble bees are 2 to 3 times larger than honey bees, they are neither as aggressive nor as abundant as the honey bees, and therefore not as dangerous.

Avoidance/Control. The best way to avoid Hymenoptera stings is to prevent human contact with these insects. This is especially important for persons hypersensitive to bee venom. Some preventive steps are:

1 Avoid outdoor activities in unfamiliar areas where stinging insects are known to occur.

2 When outdoors, don’t use floral-scented cosmetic products or leave sweet beverages or foods exposed in areas where they might attract bees.

3 Avoid garbage collection areas, which attract Hymenoptera.

4 When outdoors, always wear shoes and, if possible, a long-sleeved shirt, long pants, or other protective clothing. Don’t wear clothing with a bright floral print or loose-fitting clothing in which stinging insects may be trapped.

5 Don’t make rapid movements around stinging insects or intentionally disturb either the insects or their nests.

6 Eliminate all Hymenoptera nests around inhabited areas (wild honey bee colonies may be removed by a local beekeeper). When necessary, an insecticide such as 5% carbaryl dust may be applied in a nesting area within a building to eliminate the nuisance colony.

7 Educate young children on the hazards of venomous arthropods.

Envenomization Reaction/Treatment. (See appendix.)

3. SCORPIONS (Class: Arachnida; Order: Scorpionida)

Identification. Scorpions are crablike in appearance, with pincers attached to their two front appendages. They also possess a five-segmented “tail” terminating in a bulbous structure with a prominent stinger. The body size of mature scorpions varies from 2 to 10 cm (0.8-4 in) or more, depending upon the species.

Distribution. Scorpions are most prevalent in warmer climates. In the United States the two most dangerous scorpion species, Centruroides sculpturatus and C. gertschi, have been found only in Arizona.

Biology/Behavior. During daylight hours scorpions hide under objects or debris on the ground. At night, they come out of hiding to search for food, which consists primarily of ground-inhabiting arthropods. The prey is grasped with the pincers and stung by rapidly bringing the stinger forward directly over the head. This quick stinging motion is also used for defense, as is usually the case with human envenomizations.

Avoidance/Control. To avoid stings in scorpion-infested areas: remove accumulations of boards, rocks, and other debris; wear leather gloves to remove any item from the ground; inspect and shake out clothing or shoes before donning them; and when moving about at night, turn on lights to avoid contacting these nocturnally active arthropods. Insecticides that are commonly used for household cockroach control are also useful for controlling scorpions. Special care should be taken to treat around all baseboards thoroughly.

Envenomization Reaction/Treatment. (See appendix.)

4. VELVET ANTS (Order: Hymenoptera; Family: Mutillidae)