Widow spiders (Genus Latrodectus) are the best known and largest of the Cobweb Weavers (Family Therididate). All widows are venomous and they inhabit most warmer regions of the world to a latitude of about 45 degrees N. The species L. Hesperus is common in the western US and is the Black Widow found in the North American deserts. L. Mactans is the Black Widow common in the eastern and central US. The Brown Widow Spider, L. Geometricus, is also found in the US. The female Black Widow is shiny black, usually with a reddish hourglass shape on the underside of her spherical abdomen. Her body is about 1.5 inches long. Adult males are harmless, about half the female’s size, with smaller bodies, longer legs and usually have yellow and red bands and spots over the back, as do the immature stages. Newly hatched spiderlings are predominately white or yellowish-white, gradually acquiring more black and varying amounts of red and white with each molt, Juveniles of both sexes resemble the male and are harmless.
4 [; L0 e2 l. b- M Adult male Black Widows wander in search of females but do not feed or bite. They are not often seen because they are usually eaten by the female after mating. The female then lays several batches, containing up to 750 eggs each, in one summer. The egg case, about 1/2 inch in diameter, is suspended in the web. It is white to tan in color and has a paper-like texture. There may be 4 to 9 egg sacs produced during a summer. Normally, only 1to 12 young survive after the egg incubation period of 14 to 30 days due to cannibalism.
$ C; y, l6 E/ P$ _: _" j1 U# I8 ?( o The venom of the black widow spider is 15 times as toxic as the venom of the Prairie Rattlesnake. But only a minute amount of the toxin is injected with a single bite by the spider, so they are rarely fatal. However, the relatively large amount of injected rattlesnake venom results in about 15 to 25 percent mortality among those bitten.* X1 l4 z* u U- r
Be very careful when working around areas where black widow spiders may be established. Take proper precautions-wear gloves and pay attention to where you are working. The reaction to a Black widow bite can be painful, and the victim should go to the doctor immediately for treatment. To control the black widow, carefully remove all materials where they might hide. They can be cleaned out of an area simply by knocking down the webs, spiders, and round, tan egg sacs with a stick and crushing them underfoot. Removal or destruction of the egg sacks may help control the population. This spider is resistant to many insecticides.
, A4 b. k) d" b2 Y 11. The word “venomous” in line 2 is closest in meaning to2 u# Z6 J: o7 i+ Q# d7 @2 q
a. Cannibalistic
6 ?( ^; z8 a B b. Like warm climates
7 E$ U2 I0 K% L3 H c. Poisonous
4 b( a! V7 w3 H8 P- x d. Lives at 45°latitudes: d3 B6 C# `7 @1 c
12. The word “minute” in line 9 is closest in meaning to
& c2 T' g6 Q- e' {% Q a. Tiny
" ^. F) [2 G g: |! S b. 60 seconds
( O, @+ Q* V7 ]# V0 i c. Drop
" C E$ ` x" z/ \3 Q d. Harmless
2 U! g8 j4 w' x2 ~' ]% e1 A 13. What according to the author are 2 general suggestions from those who may be concerned about black widow spiders? |
发表于 2012-8-14 23:21:39
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