How long do black widow spiderlings stay whiteish in color? How long is it until they first molt?

Question

I found and caught a mature black widow in our small back yard area a few weeks back, later killed it. Since then, I've found others around as well. I've sprayed (though I think I need to get something more potent to get rid of them). I've been checking diligently around when outside and watering. Though I haven't noticed any egg sacs, tonight I found a white black widow spiderling crawling around.

Answer 1

Black Widow spiders molt several times, including once before they hatch, this takes about 4 weeks.  Then after 2-4 months they molt again and are sexually mature enough to breed.  They molt several times in their life and even after reaching adult hood.

Black Widow Spider = Latrodectus mactans

Ohio State Fact Sheet:  http://ohioline.osu.edu/hyg-fact/2000/20...

"Mating takes place in spring or summer. A common misconception is that the female usually consumes the male after mating. Such behavior rarely occurs. The female lays eggs in a silken sac that is globular shaped and about 1/3 to 1/2-inch diameter. Sacs are white at first, later turning tan or gray. Each sac contains 25 to 250 eggs, and several egg sacs may be produced over the course of a summer. The egg sacs are suspended in the web and guarded by the female. The egg incubation period usually lasts about 4 weeks. The spiderlings hatch and molt (shed their skin) one time while inside the egg sac. They then disperse by ballooning—extruding silk threads and being transported by air currents. Their growth to maturity requires 2 to 4 months depending on the availability of prey. Spiderlings molt several times before reaching maturity....

There are many labeled pesticides for spider control. Some are labeled for homeowner use, while others are labeled only for the licensed, certified pesticide applicator.

Insecticide treatments should be applied so that the chemical contacts spiders in their webs. A non-repellent insecticidal dust is useful to treat webs because the dust clings to the silk and is likely to be contacted by the spider. Individual exposed spiders can be killed with a non-residual aerosol spray, but any egg sacs will be unaffected.

A wettable powder or microencapsulated formulation of a residual insecticide can be applied to corners, behind and under furniture, behind stored items, etc. to prevent establishment of new spiders.

Residual liquid sprays applied to the outside perimeter of the home are not very effective because of the black widow spider’s web-sitting behavior. "

According to Animal Diversity Web:  http://animaldiversity.ummz.umich.edu/si...

"Most spiders live for one year."

According to the Big Zoo:  http://www.thebigzoo.com/Animals/Black_W...

"Young black widow spiders resemble the males. Adult males and spiderlings are harmless....

Mud-Dauber Wasps are natural predatorsWhat does predators mean? of black widow spiders. Alternating warm and cold weather in the winter and spring are detrimental to their survival....

The eggs hatch in 14 to 30 days after which only 1 to 12 of them will survive due to cannibalism. The spiderlings leave the web after they have hatched. They mature in 2 to 3 months and, during that time, will molt from 3 to 8 times. "

So only the mature female is dangerous; but they are the only ones who are black with the trademark red hour glass on the belly.

According to Black Widow Spider - Latrodectus mactans:  http://www.cirrusimage.com/spider_black_...

"A female black widow spider can produce four to nine egg sacs in one summer, each containing about 100-400 eggs. Usually, eggs incubate for twenty to thirty days. Rarely, do more than one hundred survive through this process. On average, thirty will survive through the first molting, due to cannibalism, lack of food, or lack of proper shelter. It takes two to four months for black widow spiders to mature enough to breed, however full maturation typically takes six to nine months. The females can live for up to five years, while a male's lifespan is much shorter. Contrary to popular belief, the female only rarely eats the male after mating, and L. mactans is the only black widow species for which this form of sexual cannibalism has been observed in the wild. "

According to Bug Guide:  http://bugguide.net/node/view/26336

"Latrodectus mactans is exclusively carnivorous and antagonistic. Ordinarily it feeds on insects; however, it also consumes wood lice, diplopods, chilopods and other arachnids. Usually, the black widow spider enswathes prey caught in its snare, bites it, and later drags it to its hub, or retreat, to be eaten. Latrodectus mactans inflicts a small wound on its prey, uses its cheliceral teeth to mash it up, pours digestive enzymes on the prey; and sucks up the resulting food. The whole digestion process takes place outside the spider’s body....

The female lays eggs onto a web where they are camouflaged and guarded. A female black widow spider can produce nine egg sacs in one summer, each containing about 400 eggs . Usually, eggs incubate for 20-30 days, but more than 12 rarely survive through this process, due to cannibalism. It takes two to four months for black widow spiders to mature. The female live on for 180 days after maturing, while a male only lives on for another 90 days. "

The page continues to say:  "While Latrodectus mactans is not aggressive and does not have the instinct to bite."  However, I have seen a TV show on PBS that claimed the opposite; Black Widows are mean.

The article also says that Black Widow venom is more toxic than rattlesnake venom, but of course it depends on the amount of venom that gets injected.  "The Black Widow is considered the most venomous spider in North America, and it is reported that the venom of Latrodectus mactans is 15 times more toxic than a rattlesnake’s."

According to NationMaster-Encyclopedia:  http://www.nationmaster.com/encyclopedia...

"A female black widow spider can produce four to nine egg sacs in one summer, each containing about 100-400 eggs. Usually, eggs incubate for twenty to thirty days. Rarely do more than one hundred survive through this process. On average, thirty will survive through the first molting, due to cannibalism, lack of food, or lack of proper shelter. It takes two to four months for black widow spiders to mature enough to breed, however full maturation typically takes six to nine months. The females can live for up to five years, while a male's lifespan is much shorter. Contrary to popular belief, the female only rarely eats the male after mating, and L. mactans is the only black widow species for which this form of sexual cannibalism has been observed in the wild. Lifespans depend upon environment, with shelter being the greatest determining factor and food the second greatest....

There are various parasites and predators of widow spiders in North America, though apparently none of these have ever been evaluated in terms of augmentation programs for improved biocontrol. Parasites of the egg sacs include the flightless scelionid wasp Baeus latrodecti, and members of the chloropid fly genus Pseudogaurax. Predators of the adult spiders include a few wasps, most notably the blue mud dauber, Chalybion californicum, and the spider wasp Tastiotenia festiva. Other species will occasionally and opportunistically take widows as prey, but the preceding all exhibit some significant specific preference for Latrodectus."

There is come clear differences here, one article claims a live span of 1 year, while another claims up to 5.  I read one article that said a South African species was studied, but the scientist didn't determine when they molted, but only when the red hour glass formed.

Several species of wasps prey on spiders, but they may not be a good solution and have never been studied as a bio-control method.  Your best bet is to spray the web itself and any where that you think webs might be.