Dangerous Animals Week, Part II

Black Widow Spider (Source)

I bet that image caught your eye!  There is no mistaking a female black widow spider.  When you see one, it is startling.  They are so black and shiny, they stand out against any background.  In my opinion, the extreme blackness of black widows is their most charismatic characteristic - even more so than their red markings.  They are the same black as Wonder Woman's hair.  Their red markings are more variable than you learned in third grade.  Yes, they commonly have a red hourglass under their abdomens, but by the time you notice the red abdomen, you've gotten really close and you've turned over the spider, and it's too late!  Several species of black widow have red splotches on the dorsal side of their abdomens, but the southern black widow has no dorsal splotches.  If you see a jet black shiny and fairly large spider, don't pick it up!

I saw two black widow spiders this week on the farm.  That makes five so far this summer.  I've come to expect them in the drier areas of the farm, like inside the hoop house and the barn.  They also seem more likely to be present on human-made structures, like the irrigation equipment, though this week's spiders were low to the ground on plant stems.  Can you see the black widow in the picture below?

Yes, there is a black widow here.

Here I have zoomed in on the unlucky black widow:

There it is!

When you encounter a black widow, you will notice a rather strange spider web.  Black widows weave chaotic, disorganized and somewhat sparse webs.  Their silk seems to be stronger than other spiders if you happen to put a finger through a web.  The silk has been tested, and it's not stronger, but it is very sticky and somewhat thicker than what other spiders extrude.

For a person who, as a child, thought black widows were always on the hunt for an unsuspecting human to bite, real-life black widows seem shockingly meek.  They cower if their webs are disturbed.  They don't jump or run, but they hold still and hope their warning coloration convinces you to just go away.  The spider above seemed to crouch with it's little legs over its head and quiver when I uncovered it.  I was sorry to kill it, but their bites are so dangerous, we can't tolerate them on the farm.

When you look up black widow spider bites, the medical sites reassure you that 'black widow spider bites are rarely lethal'.  Thanks - that makes me feel a lot better!  Actually, I, personally, am not at great risk, but a bite to a child, elderly person or ill person can be fatal.  Black widows produce a very potent neurotoxin that can spread through the body.  It can produce systemic symptoms like fever, sharp pains, nausea, tremors and worse.  The actual bite location itself will be relatively unimpressive, with a small, red, swollen area.

Most black widow bites are not treated with antivenom (aka antivenin, if you're using the French-derived version of the word).  The antivenom is problematic because it is rarely stocked at hospitals, and it's made from horse serum, which can cause major allergic reactions.  If you are bitten by a black widow, treated with antivenom, then bitten by a rattlesnake, you will be in big trouble.  Rattlesnake antivenom is also made with horse serum, and after your first exposure, your immune system will react much more strongly to the second exposure of horse serum.  Use of antivenom can save the life of an at-risk individual, and it can shorten the flu-like symptoms of a healthy person. 

Black widow spiders get their names from one of the behaviors observed in the female black widows.  Sometimes after mating, female black widow spiders eat the male black widow.  Male black widows generally get the short end of the stick in life.  They are very small, their coloration is drab and they don't have enough venom in their bites to bother anyone.  Their main job in life is to mate and pass on their genes, and after that, they may as well provide a little food to the mother of their children.

Now that the days and nights are getting cooler, I've noticed that the cold-blooded animals on the farm have slowed way down.  The chiggers and ticks seem less intent on making life annoying.  The bees and wasps have mostly disappeared.  The black widows have finished laying eggs and have hopefully lost the strength to push their fangs in through the calloused skin on my hands.

Dangerous Animals Week, Part I

Even farmers go on vacation.  Especially when they get married and go on a honeymoon!  We went to Florida over the weekend, and I took the chance to get to know our gelatinous friends of the sea, the jellyfish and comb jellies!  There are many great mysteries in the ocean, and these critters are some of the least understood - even by Biologists.  I suppose even I have been avoiding them all these years.  I have been so blind.

Jellyfish, corals and sea anemones are all members of Phylum Cnidaria (silent C), which means they are radially symmetrical and have venomous stinging structures.  Comb jellies are members of Phylum Ctenophora (also silent C), which means they are also radially symmetrical but have comb-like cilia and are carnivorous.

I pretty much assumed that everything gelatinous and floaty in the ocean would leave painful welts that would become infected and lead to a costly doctor's appointment.  Wrong!  Many jellyfish have such weak stings that humans can't be punctured.  In fact, the ones I most often see in Florida are mostly harmless to all humans except the most thin-skinned.  The cannonball jellyfish, can apparently cause heart problems if you rub your eyes on its short tentacles, but you can pick it up or brush into it with no problem.  The moon jellyfish, according to the guide to Florida jellyfish that I read while on our honeymoon, do not sting humans.  I did not test this myself, but I did manage to convince my husband to pick one up, and it did not sting him.  Subsequent reading about this species reveals considerable difference of opinion about the the moon jellyfish's ability to sting humans, but the most reliable-sounding Internet sources say it can only mildly sting thin skin.  I chalk the reports of dire consequences up to general fear and misinformation about jellyfish. 

Cannonball Jellyfish

Cannonball Jellyfish

Comb jellies most definitely cannot sting.  Reports are unanimous about this, and I tried it out myself.  Below is a brown comb jelly in the water, and below that are two brown comb jellies in my hand.  Comb jellies are shaped rather like a stocking cap with rows of cilia along the long axis.  Those cilia reflect the sunlight beautifully.  Comb jellies can open and close one end of themselves, depending on whether they are eating something or not.  Since comb jellies are transparent, you can see what they have eaten.  Brown comb jellies eat American comb jellies, which are smaller and colorless.  I watched a brown jelly, which had obviously already eaten once already that day, engulf an American jelly in 5 seconds flat.  Once the prey was inside, the brown jelly sealed itself and probably spent the rest of the day digesting and absorbing its two meals.

A swimming (or is that hunting) brown comb jelly.

A brown comb jelly temporarily collapsed into a pile of goo in my hand.

Brown comb jelly in better light with tree reflection.

Of course, many jellyfish can sting in a major way.  The box jellyfish hurt badly, and some found in Australia are deadly.  The man-of-war can put you in the hospital (incidentally, there is a jellyfish called the by-the-wind jellyfish that looks much like a man-of-war but can't sting people).  There are sea wasps, sea nettles, lion's mane jellyfish and more.  I don't recommend learning which are dangerous by trial-and-error.  Here's a good .pdf guide to Florida jellyfish.

My other major misconception about jellyfish and comb jellies is that they can only stupidly float wherever the current takes them.  Again wrong!  While they are certainly not strong swimmers, jellyfish and comb jellies can move toward and away from things like light, movement, smells and salinity differences.  It's true they don't have brains, but they do have nervous systems to sense the environment and coordinate movements.  Some jellyfish even have fairly complicated camera-type eyes!  Many jellyfish only have to concentrate on staying upright.  Others, like the cannonball jellyfish above, can swim quickly up and down in the water to find food.