Spider Sunday: Western Black Widow

The first time I encountered a black widow was in the desert of eastern Oregon. I cannot recall the circumstances exactly, but I was rather awed, given that I had read about them but never seen one until then. Thanks to the book How to Know the Spiders, by B. J. Kaston, I learned the species found in the Pacific Northwest is the Western Black Widow, Latrodectus hesperus.

Eventually, I was able to easily identify black widow webs, even if the spider was not present. Black widow webs are large, three dimensional tangles of extremely strong threads. The whole web can easily occupy a cubic foot or more, and you can pluck the silken strands like guitar strings without them breaking. A funnel-like retreat is usually seen going into a rodent burrow, under a boulder, or some other cavity that would take heavy machinery to break into. Black widows do not want anything to do with larger animals. Only at night are you likely to see the spider out on her web.

Believe it or not, black widows begin their lives as largely *white* spiders. They lose the pale spots and stripes as they age, but because males mature more quickly, in fewer molts, they never lose their pale markings entirely. Even the immature spiders sport at least some semblance of an “hourglass” marking on the underside of their abdomen, so you can still identify them as widows. Since widows sit upside down in their webs, that hourglass marking is usually visible.

The Western Black Widow is the largest North American member of the genus Latrodectus. Females have a body length of 14-16 millimeters as adults, males 7-8 millimeters. Mature females usually lack any red markings besides the hourglass, and that may be broken or even wanting in some specimens. Some individuals may be chocolate brown instead of black.

Mature males are recognized by their swollen pedipalps, which resemble tiny boxing gloves located near the spider’s face. He uses these as intromittent sex organs that fit like a key in the “lock” of the female’s paired genital openings. Contrary to popular myth, the female does not always cannibalize her mate, though sex is a risky business for nearly all male spiders.

Mated females can produce several egg sacs in their lifetime, each containing up to 750 eggs. Few of the spiderlings that emerge will make it to maturity themselves, due to cannibalization by siblings and other natural hazards. Adult females can live more than a year, though.

Western Black Widows are able to secure surprisingly large prey. Their webs are designed to trap prey walking over the ground. When a victim stumbles into one of the sticky trip threads attached to the ground, the thread breaks and rebounds, yanking the potential prey animal into the main body of the web. The trip threads are so elastic and strong that even small vertebrates can be captured in widow webs. I personally witnessed a hatchling lizard struggling in a web. Yes, I intervened.

While black widows have no problem killing prey as imposing as large beetles, they flee rapidly when they sense a larger creature such as a human. The speed at which they can scramble back into their retreat is astonishing. I have had many a photo opportunity cut short when I accidentally bumped a thread.

The Western Black Widow is a very common spider found from extreme southern British Columbia south to Mexico and west to Kansas, Oklahoma, and Texas. It is particularly abundant in drier habitats such as deserts and prairies, though it can be encountered in more damp situations as well.

Because of the timid nature of widows, it is relatively easy to minimize the possibility of being bitten. Simply take these precautions:

• Never leave clothing, shoes, or gloves outdoors overnight. A spider can seek shelter during that time.
• Do not put your hands or feet where you cannot see into, such as holes and crevices, inside the mailbox, or behind large objects that have been in storage for awhile.
• Carefully inspect firewood, houseplants, toys, etc being brought indoors from outside in case a spider may be hitchhiking on the object.
• Do not walk barefoot outdoors, especially at night.

Reactions to bites from widows can vary considerably from one person to the next because immune system responses to envenomation are highly individualistic. The spider may not even deliver much, if any, venom. Still, they typical experience is excruciating. The venom is neurotoxic, meaning it affects the nervous system. This translates to triggering constant muscle contractions that result in severe cramps, especially in the abdomen, legs, and other large muscle groups. One friend of mine had back spasms for months following a black widow bite. One should always seek emergency hospitalization immediately, precisely because one cannot be sure how their body will react. Antivenin is available for treatment, though it is recommended as a last resort by most hospital physicians. Antivenin is produced from horse serum, which can carry its own complications including allergic reactions. Obviously, avoiding bites is preferable to treating them after the fact.

Black widows cannot be easily “controlled.” Contact insecticides have a very low probability of reaching a hidden spider, and killing one spider means it will soon be replaced by another anyway (prime web sites are a coveted commodity). Meanwhile, the spiders will kill plenty of pest insects that could potentially be more trouble than the spiders themselves. By all means, do inspect playground equipment and toys before allowing your children to play outdoors. It all comes back to vigilance and prevention. Take care, but value the work your spiders do.

The Germans Are Back

The other day I came out of my apartment to find a piece of paper stuck in my screen door. I was dreading reading about a rent increase, but the announcement was unpleasant in a different way. “We are starting a new program here at (name of apartment complex)” began the notice. Turns out that the management is initiating an ongoing pest control schedule, no doubt due to someone complaining about German Cockroaches, Blattella germanica.

I have had German roaches in my own apartment previously. Initially I did not treat for them because a Mediterranean House Gecko, Hemidactylus turcicus, had also taken up residence in my kitchen and kept the roach population to tolerable levels. Eventually, the lizard died, and then the roach population exceeded my psychological and physical “carrying capacity.”

I reluctantly purchased some roach bait traps, and that did the trick….until a few months ago, when I saw another roach. In the last month I have killed two: a male and a female. Still, I have a hard time with the invasion of privacy that comes with an extermination service, not to mention having some trepidation over whatever chemical treatment they are applying.

Ok, enough about me, how about some background on the German Cockroach? It is believed that most of our “domiciliary” roach species are native to tropical Africa, and can only exist outside their normal geographic range by occupying buildings that offer a year-round approximation of their tropical homeland. Why are they called “German,” then? Well, here in the United States at least, we have a history of naming economic pests after nationalities that we have had conflicts with. So, given our World War II enemies, it seemed fitting to apply the “German” epithet to this particular roach species (in Germany the species is called the “Russian” Cockroach).

The German Cockroach is one of the smaller roach species, ranging from 11-13 millimeters in length. Consequently, it is sometimes mistaken for some other kind of insect and dismissed. There is no ignoring their numbers, however, and opening a cupboard can send dozens of them scurrying for darkness in a dwelling that is infested with them. Males are sleek, slender, amber-colored insects, while females tend to be darker and more robust. Both genders are shown in the images here. See if you can tell which is which.

As far as I am aware, domestic pest roaches have only been implicated in the mechanical transmission of bacteria, never actually proven to be carriers of Salmonella and other treacherous microbes. Roaches groom themselves constantly, lest they themselves become victims of pathogens and fungi. This is not to say that cockroaches are at worst a nuisance. Far from it.

What has been conclusively demonstrated is that cockroach body parts, shed exoskeletons (remember roaches have to molt to grow), and fecal matter are a major, major trigger of asthma, especially in children. This is one reason that neglect of public housing should be a crime: improper maintenance can lead to chronic health issues that are far more costly to society (and the individual) in the long run. Also, entomologists who study roaches in the lab frequently develop allergies to roach exoskeletons, feces, and body parts. Such afflictions are sometimes severe enough to cause the scientists to abandon roaches as study subjects.

Cockroaches are successful organisms for several reasons. They achieved near perfection in the evolutionary sense millions of years ago, judging by the fossil record of roaches that are essentially identical to contemporary species. They are generalist feeders, able exploit all manner of organic matter. They are adept at detecting and avoiding poisons, being able to taste-test food before ingesting any. They reproduce at a rate that makes rabbits envious.

Female German Cockroaches cannot be accused of parental neglect. Once mated, a female will produce an egg capsule called an “ootheca.” Each ootheca contains an average of 30-40 eggs. The female carries the capsule at the tip of her abdomen until just before the eggs are ready to hatch. Then she carefully deposits the egg case in a crack or crevice where the cockroach nymphs can emerge in relative safety. Each female roach can produce several ootheca during her lifetime.

A typical roach population is a youthful one, comprised of about eighty percent nymphs of various stages and twenty percent adults. I haven’t seen any nymphs in my home lately, and I hope it stays that way.

Wasp Wednesday: Ancistrocerus tuberculocephalus

I can always count on an aphid-infested tree to provide me endless hours of enjoyment. Aphids secrete a sweet, liquid waste product called “honeydew.” This substance attracts an enormous diversity of wasps, bees, flies, and other insects (even butterflies). I found just such a tree, a young aspen, at the Cheyenne Mountain Zoo in Colorado Springs, Colorado last week. Among the numerous hymenopterans seeking refreshment was a mason wasp that goes by the unfortunately long name of Ancistrocerus tuberculocephalus.

Mason wasps are solitary members of the family Vespidae, which includes familiar social species like yellowjackets and paper wasps. Nearly all members of that family fold their wings longitudinally when at rest, so that behavior is often a good way to identify them.

While some of the mason wasps make free-standing nests of mud, the majority nest in pre-existing cavities, partitioning the interior space into separate cells.

Ancistrocerus tuberculocephalus is known to use the abandoned mud nests of the Black and Yellow Mud Dauber, Sceliphron caementarium, for its own nests. It can also dig out the pith in sumac twigs and nest inside the resulting hollow; or it can use old beetle borings in dead wood. The female wasp provisions each cell with paralyzed caterpillars that will be the food source for the single larva that develops in each cell.

This species is divided into two subspecies. A. tuberculocephalus sutterianus ranges from British Columbia to California, Nevada, and Utah. Below is a specimen of this subspecies from near Long Beach, California.

A. tuberculocephalus tuberculocephalus occurs from South Dakota and Wyoming to Utah, Colorado, Arizona, New Mexico, and west Texas. The remaining images in this post are of specimens from Colorado Springs.

You can help provide housing for these flying pest control agents by simply leaving old mud dauber nests where they are. Should you be feeling more industrious, consider bundling old sumac twigs and hanging them under an eave;

or drill six-inch holes of various diameters into a block of wood and tack it up.

Many solitary wasps, and bees, too, need the extra real estate these days as their habitats disappear amid suburban sprawl. The wasps won’t bother you, and you might make some interesting discoveries about them.

Special thanks to David R. Green for use of his image of the twig trap nest, complete with a solitary wasp peering out of it. Thanks also to "Birds n' Such" for the image of the upscale bee block.

Spider Sunday: Wolf Spider

While living in Massachusetts in 2009 I had the pleasure of prowling around some very nice natural areas with Lynn Harper, an accomplished naturalist who works for the Natural Heritage and Endangered Species Program in the Massachusetts Division of Fisheries and Wildlife. Among the places I went with Lynn was Tully Lake in Royalston. There I was to encounter a very large wolf spider in a wet meadow near the lake.

Scientists have not made it a priority to assign common (English) names to individual species of insects and spiders, unless the creature is of economic significance. Consequently, there is no specific name for this magnificent, eye-catching arachnid. It is probably the species Hogna helluo, though without a thorough physical exam of the specimen it is nearly impossible to be certain. Spiders darken with age, and there is plenty of variability in color and pattern from individual to individual anyway.

Wolf spiders comprise the family Lycosidae, and most of the large North American species belong to the genus Hogna. They used to be classified in the genus Lycosa, but a revision of that genus resulted in the finding that there are no New World species in the genus Lycosa. North American species were thus reassigned to Hogna.

Arachnologists measure spiders by body length, not legspan, but even by that standard, Hogna are real giants. Mature males of H. helluo range from 10-12 mm, while females are a whopping 18-21 mm. Add the sprawling legs and they are an intimidating creature to those unfamiliar with their skittish nature.

Wolf spiders in general hunt “on foot” instead of building webs to snare their prey. Consequently they are more muscular than the average arachnid, with keen eyesight. They are most active at night, perhaps because their arch enemies the spider wasps (family Pompilidae) hunt during the day. Try hunting for wolf spiders yourself, at night. Shine a flashlight or a headlamp over a field, or even a lawn, and you will see the eyes of wolf spiders sparkling like diamonds as they reflect the beam of your light.

Wolf spiders can simply overpower their prey, and if you witness one attacking a cricket or other insect you will probably be shocked by the violence. Still, a wolf spider is going to flee at top speed from your approach. I was fortunate to reel off a number of pictures before this female fled among the grass and moss.

There are many stories to tell about wolf spiders, so I will give away no more secrets today. I will simply encourage you to go out and look for them yourself; and ask that you treat the odd wolf spider that enters your home with a little respect. Please relocate such spiders back outdoors where they can intercept invading insects that could do you, your family and pets real harm. Thank you.