Northern black widow outbreak?

That’s the question that two reporters from the northern Lower Peninsula asked me this week. Apparently, many people in this area of the state are finding this spider around their homes and several reported finding many of them. I have never thought of spiders as having outbreaks, like the army worms discussed above. I can’t imagine what the reaction of people, who are prone to arachnophobia anyway, would be if armies of black widow spiders were seen marching across the countryside destroying everything in their path. Outbreak is a relative term that depends on the perceived threat of the bug. Maybe finding a dozen or so widow spiders in one’s yard is the functional equivalent, outbreak-wise, of having a million or so army worms devouring your cornfield. Anyway, outbreak or not, it appears that northern black widow spiders are more numerous in certain parts of the state than in past years.

The northern black widow spider, Latrodectus variolus (Araneae: Theridiidae), is found throughout the eastern United States, from southern Canada south to Florida, and west to eastern Texas, Oklahoma and Kansas.  In Michigan, they appear to be more common in the western Lower Peninsula. Outdoors, they are found in old stumps, hollow logs, under fallen fence posts, in abandoned animal burrows or piles of brush, and in the corners of sheds and crawlspaces. In the northern black widow, the distinctive hour glass marking on the underside of the abdomen is incomplete or split in the middle. Northern widows also have a series of red spots along the dorsal midline of the abdomen, and many have a series of lateral white stripes on the abdomen. The web of the black widow is an irregular mesh of strands in which the spider hangs in an inverted position. 

Surprisingly, as common as this spider is, black widow bites are infrequent because the spider is actually very timid and prefers fleeing when disturbed. That’s a good thing because the venom of a widow spider is 15 times more toxic than that of rattlesnakes. However, due to the small amount of the venom injected into the bite, widow bites are far less serious. There is less than one percent mortality (mostly children) of persons bitten by black widows. The toxin affects the central nervous system and the severity of the bite depends on many factors including the age, size and sensitivity of the victim, location and depth of the bite, and when the spider last used her venom. Pain is felt almost immediately after the bite, and increases for one to three hours, but may last for 24 hours. In severe cases, large muscles become rigid with spasms, there is a rise in body temperature, blood pressure, profuse perspiration, and a tendency to be nauseous. If a person has been bitten by a widow spider, keep the bite victim calm and under observation. Immediately take the victim to a doctor or emergency room. If the spider can be safely captured, take it to the doctor for verification of the type of bite. The bite victim may need to be hospitalized. Fatalities are uncommon and healthy victims usually recover quickly.

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