BLACK WIDOW SPIDERS (LATRODECTUS) IN VERMONT

        During November two people came to the museum with female black widow spiders they had found in their homes, one climbing a living room wall in Randolph and one in a basement in Burlington. Since we have no VT specimens in the museum collection we thought this might represent a population surge in species normally found in warmer climates. Perhaps this is an indicator of global warming in VT, but, whatever the cause, we should become more aware of this spider.
        Description- They are black spiders with long tapering legs. The abdomen is globose and the overall size for females ranges from 8-13 mm. (3/4" in) while the males are smaller (3/8"). They make haphazard webs with a retreat tunnel at one end and are usually found outdoors under rocks, bark and around outside sheds. They could be  inadvertently brought inside with firewood, lumber or some camping equipment.
        Number of species- There are two eastern species called Latrodectans mactans and variolus and there is a western one called hesperus which may be brought in with produce (eg. Grapes). The definitive markings are the red hour glass pattern on the underside (ventral) of the female. The males do not have an hour glass mark but rather scattered red & white spots over both sides of the abdomen.  The females also have a distinctive scattered pattern of markings on the dorsal side that can help in recognition.
 

Anterior ventral, Latrodectans mactans Anterior ventral, variolus Anterior ventral, hesperus
Posterior Posterior Posterior

Dorsal view below:

        The Bite- Males do not bite. Although these spiders are not agressive, the females will bite if threatened.  The venom is a neurotoxin which affects nerve-muscle conduction and contraction. Even though the site of the bite does not become inflamed or swollen, you could notice the physiological affects of the neurotoxin. Abdominal muscle contraction causes painful cramps and the muscles used in breathing become paralyzed. This is accompanied by increased blood pressure, fever, sweating and a dry mouth & possibly swollen eyelids.  The bite is usually not fatal but there have been more cases of severe reactions in infants, children, the elderly or ill persons. The venom   in all species is the same but amounts can vary dependent on the age of the spider and its condition.  The victim should see a doctor. Recovery usually takes about 5 days.
        So, if you see a possible black widow in your house it is better to kill it or trap it in a small vial or bottle and put it in the deep freeze. Later add some rubbing alcohol to the container and bring it to Dr. Bell at the Bio. Dept.  (656-4349) It would be valuable to have documentation of this species in Vermont.

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