Special Sub-Topic: The Black Widow Spider
|Widow spiders are found throughout the world but the primary habitat for the black widow is North America. Which of these species is NOT one found in this area?|
red-backed spider (Latrodectus hasselti). The red-backed spider is found in Australia and is another dangerous member of the family. The northern widow can be found in the northeastern U.S and southeastern Canada. The southern species ranges from Florida to New York and west to Texas, Oklahoma and Arizona. The western species is found in the western U.S, southwestern Canada and much of Mexico.
|The female black widow is known for having a red hourglass shape on the underside of her abdomen. How are the male spiders marked?|
yellow and red bands with spots on the back. The male spider is usually marked with yellow and red bands and spots on his back, the same as immature stages of the spider. Males are about half the size of the female with smaller bodies and longer legs. Newly hatched spiderlings are mostly white and acquire black and varying amounts of reds as they molt.
|The female widow spider produces silk for her web and for the 4-9 egg sacs she lays per year. What type of web and consistency of silk does she have?|
large irregular web, strong silk. The female widow has very strong silk and weaves her webs in irregular,large cobwebs which are rough and sticky. She is very solitary and shy. Webs are constructed in quiet, dark places and she will hide within the web. Only if disturbed will she move and possibly bite.
|What time of year does the female widow lay her egg sacs?|
summer. Sacs are laid in the summer. After hatching and with several moltings, the spiderlings mature through the summer and fall. By winter they are considered subadults. They become sexually mature in the spring and mate in the very late spring.
|Of the several hundred eggs per sac, less than a dozen will survive to maturity. What is the most common reason that so many eggs are lost?
cannibalism. Most are victims of cannibalism from the other spiderlings. Those that survive attach to a string of silk and balloon on air currents to disperse. Temperature, humidity and availability of prey are other factors that determine their survival.
|The female widow gained her reputation and name from the custom of eating her partner after mating. In reality, this rarely happens.|
True. In reality, this rarely happens. When it does, it is usually because the male can not get away from her fast enough. If he stays too long, she mistakes him for prey and attacks. Her reputation is believed to be an artifact of the conditions where early studies of her behavior were observed. The spiders were usually kept together in small containers and the male had no opportunity to leave, thus he became a meal.
|The female black widow is one of the most poisonous creatures with venom more potent than coral snakes, cobras or rattlesnakes. However her bite is rarely fatal in humans. Why not?|
both of these. The bite is fatal less than 1% of the time. Though very potent, the chelicerae, which deliver the venom, are not very large and don't penetrate the skin that deeply. Often she will bite and not deliver any venom at all. Before the development of antivenin, the number of fatalities was only about 5%. However, there can be severe reactions and children, elderly and very ill people especially need to be treated and monitored.
|What is the normal diet of the widow spider? |
insects. The primary diet of widows is insects. Once ensnared in the web, she punctures them and injects digestive enzymes into the bodies and gnashes them with her fangs. Once they are liquefied she then sucks out the resulting fluid. The mud dauber wasp is one insect that preys on the widow spider.
|You've been bitten by a black widow. What should you do until the help arrives?
all of these (wash the bite with soap and water, apply ice to the bite area, treat with antibiotic cream or lotion). All of these are good measures to use until you get medical attention. It is also helpful to bring along the spider if at all possible, even if it has been crushed. Symptoms vary in individuals. The initial bite might not even be felt but as the toxin spreads through the nervous system, the site of the bite might begin to have a dull, numbing ache. This ache may progress through small, then large muscle groups, particularly the abdomen. Additional symptoms may include sweating, nausea, leg cramps, irregular heartbeats, rise in blood pressure and vomiting.
|Luckily you have survived the bite of the black widow but you would like to avoid having that experience again. Which of these preventive measures does NOT work?|
spray your baseboards with pesticide. Pesticides do not usually work as the spider just avoids the areas sprayed. Spraying the spider directly will kill her over time but it is not recommended as you may end up with an intoxicated spider running loose in the house. Widow spiders do not normally invade a home unless assured of a dark, quiet area so be especially careful in attics and basements where things are stored. Outdoors, always wear protective gloves especially around woodpiles, rock, and other places that are usually dark and undisturbed. If you do find them in the home and manage to vacuum them up, remember to dispose of the bag outdoors, immediately.
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