Spider invasion, peculiar freeway foam, scars and tats forever

Heymatt:
I’ve been living in my house in University Heights for 65 years and I’ve never had a spider problem like this one. These little buggers are festooning the roof tiles like Christmas tinsel. They’re on everything in sight and, worst of all, my plants are getting all wrapped up and they are beginning to suffer damage. Unlike the beautiful web the fall garden spiders weave, this bunch makes a zig-zag web. My niece on Mt. Soledad has the same problem, so it must be citywide. The agriculture department says the spiders have always been there, but this is new to me!
— Angie

Without sending a squadron of elves out to inspect your roof tiles (which we could do, but you wouldn’t want to feed them afterward!), I can’t identify your problem spiders onsite. I can take a pretty good guess, however, that they’re brown widows. The little buggers, as you call them, are an invasive species that made their way to America’s Finest City from South Africa via the Gulf Coast. They’re cousins to our native black widows, but they’ve only been spinning webs in San Diego for about 12 years. Since the species is new in town, they lack natural predators and their population has experienced an unchecked explosion. Rest assured, if you do have brown widows in your yard, they’re a new problem and you’re right to be perplexed!

The good news is that the spider population is stabilizing, and it’s only a matter of time before parasites (spiders’ chief foes in the wild) get wise to the new widows and start taking their fair share. Nature will soon reclaim your yard for you. In the meantime, be careful because the normally shy brown widows are poisonous and will bite if provoked!

So far, the spiders haven’t expanded to the wilderness east of the city, but if anyone in the Ramona or Julian area thinks they spot brown widows, it would be good to alert the local authorities at the wildlife department or the Museum of Natural History.

Hey Matt:
I’ve noticed that after a rainstorm, when the water from my car drips onto my garage floor, there is a white, slightly fluffy residue around the tires on the garage floor when the floor dries. I’ve not noticed this before this winter. If I still lived back East, I would assume it’s salt residue from street snow removal, but for coastal San Diego, that’s not likely. I can only think this has something to do with the salt in the air, since we live a few miles from the ocean. I haven’t tasted it, since it’s on my garage floor and came from my car.
— Paul, Carlsbad

Let me first offer you a high-five, Paul, for not tasting the foamy slime that’s accumulating on the floor of your garage. As simple as it seems, such a common sense decision can be way outside the bounds of logic for so many people! You’d be in for a disappointment, anyways, because the fluffy residue in question isn’t salt. Cousin Jeb Alice (always a riot at parties) licked some for a dollar. Not briny. Tasted like road slime with flavors of gas, dirt, and hints of the sorrows of weary commuters. The fluffy bubbles are made from the soap and detergent that’s used to keep diesel engines clean. Some of it doesn’t burn off during combustion and gets poofed out into the atmosphere with the exhaust. It condenses on the road and waits for rain, then, next thing you know, soap bubbles. In European countries, where diesel autos have a bigger market share, this phenomenon is much more widely known.

Hey Matt:
If every cell in your body changes every 5 to 7 years, why do your worst scars and your tattoos stay all your life?
— Old, puzzled Pict, via email

The reason that blue-tattooed and battle-scarred Picts don’t end up with flawless skin every couple years (at which point it’s true that most of the body’s skin cells have been replaced) is twofold:

Firstly, scars can last forever because there is only so much the body can do to heal a wound. Other than in prenatal infants and animals with regenerative capabilities, wound-healing necessarily leaves some degree of permanent damage. Scars are made of fibrous connective tissue that initially serves to pull a wound closed and keep it there. Afterward, that tissue remains, sometimes forever. It’s made of the same collagen that’s in muscles and skin, but the tissue is arranged differently.

Tattoos, on the other hand, hang around for life because the deeper layer of skin into which the ink is injected is relatively stable. While the epidermis (outer layer) is sloughing off on a daily basis, the dermis is mostly connective tissue, so it’s durable enough to hold a tattoo. The droplets of ink are suspended in the tissue about 1mm below the surface of the skin, and cells divide and move around them without disrupting the appearance of the tattoo.