Don’t fear: That ‘cocoon’ is housing some good garden friends

Pam in Ashburn writes: “I have attached a photo of what I think are insect cocoons on the outside of our second-floor balcony door. I saw them for the first time today from ground level and have not opened the door since. I put some Christmas decorations out on that balcony in mid-December and did not see them then. Do you know what they are and what I should do about them?”

Yes, Pam. Those aren’t technically cocoons — although that is exactly what they look like. And ‘insects’ are not involved. Those soft, cotton-like casings are safeguarding the eggs of the next generation of some species of spider — perhaps the beautiful and highly beneficial garden orb weaver.

 

But I don’t want spiders in my house!

Pam was not happy to hear this, and wrote back: “What kind of spiders? I do not want them in my house!”

Well, they’re not in your house, Pam; they’re outdoors. And outdoor spider nests belong to outdoor spiders.

What kind of spider are the eggs incubating? Exact identification can be surprisingly tricky, but we know that the adult spider involved is about the same size as one of those egg cases; and I’m 100 percent certain that they are no threat whatsoever to you. In fact, the spiders that emerge are likely going to be very protective.

Name That Spider

First, outdoor spiders tend to stay outdoors, so when those eggs hatch, the baby spiders are going to head in the other direction.

Second, that’s not going to happen until spring, making January the ideal month to move them. There is no way they’re going to be active in this freezing cold weather.

Although I couldn’t identify the mother conclusively, they’re not black widows. Those eggs are laid in famously messy and disheveled nests in low-to-the-ground areas, such as firewood piles. (Which is where there IS a good risk of being bitten by one, which is why you should always wear heavy gloves for such jobs as gathering firewood.)

And they’re not the infamous recluse spider, which lives and nests inside homes. (And whether you want to believe it or not, they’re not found anywhere in our area, unless you just moved here from Oklahoma and they got packed with the sweaters.)

Be assured that those casings almost certainly contain the eggs of creatures that don’t harm humans, but do kill enormous numbers of pest insects.

 

Spiders are your friends

Yes, the odds are close to 100 percent that the spiders that emerge from Pam’s egg cases will be beneficial creatures that don’t harm humans but instead feed on really nasty pests, such as horseflies, Japanese beetles and the truly dangerous mosquito. Mosquitoes carry West Nile, Zika and other seriously damaging diseases that, unlike spider bites, are sadly common because, unlike spiders, mosquitoes do intentionally bite people. A lot.

So why the strong, almost universal, negative reaction to spiders?

Noted spider researcher Rick Vetter of the University of California at Riverside once explained to me that “studies have shown that 80 percent of people HATE spiders, and 4 to 8 percent have full-blown, all-out arachnophobia — an irrational fear of spiders.”

But the truth is, few spiders even have the ability to bite people (they have wrong size or type of mouth); none have the inclination to bite people (the rare bites that do occur are all accidental, such as when we step on one, or stick our hands into something, such as a firewood pile); and most ‘spider bites’ are misdiagnoses of other problems, such as mosquito or tick bites or staph infections, such as MRSA.

 

Don’t eradicate — relocate

So, what should Pam in Ashburn do?

I have similar, fluffy nurseries stuck to the outside of some of our windows every season, and I just leave them be. I know that the spiders that emerge will have no interest in me, but will eat their own weight in insect pests every day.

But I also understand the fear spiders inspire in normal people.

So if you find such cocoons on a place that troubles you this winter, just use a stick to move them to the garden or the woods. The baby spiders-to-be that are inside the eggs inside those casings will remain dormant until spring and then come out and go to work. It’s worth the little bit of effort: Spiders really are excellent pest controllers that pose almost zero threat to people.

A final thought: Imagine that every web your rescued spiders (hundreds to a single egg casing) spin will intercept hundreds of disease-carrying mosquitoes that were about to bite you.

Mike McGrath was Editor-in-Chief of Organic Gardening magazine from 1990 through 1997. He has been the host of the nationally syndicated Public Radio show “You Bet Your Garden” since 1998 and Garden Editor for WTOP since 1999. Send him your garden or pest control questions at MikeMcG@PTD.net.


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