Black widow surprise at the doorstep: Latrodectus spp.

Another common name for a black widow spider is an hourglass spider. Guess why!

Last week while tidying up a basement walkout, a colleague discovered a gorgeous and very pregnant black widow spider attempting to escape her broom. Fortunately, my colleague did not freak out and punish the spider. After glamming for the camera for a while, the widow casually strolled into a capture jar held by the dauntless homeowner. This beauty, named Lola, enjoyed a photo shoot and will soon be joining her cousins as a full-fledged member of the Insect Petting Zoo at the University of Maryland. Another name for these creepily beautiful arachnids is ‘hourglass spiders’ due to the bright red hourglass-shaped mark on the underside of the abdomen of some species.

What a surprise! A gorgeous female black widow spider making a basement walkout her home. After glamming for the camera for a few moments, she readily investigated a capture jar held in the steady hands of stout-hearted Dr. Shrewsbury. This beautiful spider, now christened Lola, will join more than a hundred of her arthropod kin in the insect petting zoo at the University of Maryland, College Park.

The black widow is arguably one of the most interesting characters in Marvel Comics pantheon of heroes and one of the most dangerous groups of spiders in the United States. The widow’s venom contains a very potent neurotoxin, alpha-latrotoxin. A measure of the toxicity of alpha-latrotoxin, an LD50 of 20 – 40 micrograms per kilogram of body weight, puts it right up with some very deadly snakes. Fortunately, widows do not always inject venom when they bite and even if they do, the quantity is exceedingly tiny. There are five species of widows in the United States, three native species and two non-native species, and they are found in every state except Alaska, but mostly in southern and western states. Widows spin loose webs in protected places such as under logs, stones, or boards, and in angles of windows and shutters. They are commonly found in dumps and in rural areas such as farms and plant nurseries where they frequent barns, sheds, outhouses, and equipment storage areas.

Having paralyzed a hapless moth with venom and wrapped her victim in silk, the black widow will feed at her leisure.

Like most spiders, the fangs of the black widow are used to capture prey and the venom injected through the fangs helps subdue the victim. Also like most spiders, black widows are not aggressive and bite humans only when harassed or accidentally pinched or grabbed. The bite of the widow is usually painless or felt as a pinprick. The more serious symptoms of the bite first appear within 30 minutes to two hours after the bite. These include back pain and muscle cramps that can be severe, rigid muscles in the abdomen, nausea, vomiting, sweating, restlessness and, in some cases, elevated blood pressure. These symptoms are most severe after 3 hours but may persist for many days.

A previous member of the Insect Petting Zoo at the University of Maryland, a gorgeous black widow named Scarlett, glides back to protect her unhatched brood in the egg case after carefully inspecting her gossamer web.

Black widows do not discriminate among their human victims, and envenomation can occur in people of any age. In the U.S., between 2,000 and 2,500 bites are reported each year with the greatest number of bites in children. Lethal bites are exceedingly rare and only three deaths have been reported worldwide in medical literature. Complications associated with black widow bites are greatest for the very young, the very old, and people with cardiovascular disease. The death rate from documented bites occurs in far less than 1% of reported cases. Rapid treatment with antivenin and other medications can greatly reduce the severity and duration of symptoms associated with a black widow bite. Unlike other spider bites, such as those from the brown recluse, there is no terrifying necrotic skin lesion at the site of the bite.

Hundreds of spiderlings hatch from a single egg sac of the black widow and each female can lay several egg sacs annually.

To avoid bites of black widows and other spiders, wear gloves and long-sleeved shirts when you work in areas that might house spiders. Try to reduce clutter such as brush piles, vegetation, trash, and rubbish where spiders might hide outdoors. Do the same for furniture, sports equipment, and clothes indoors. Carefully inspect these items before moving them and store them in containers or sealed bags whenever possible. If you are bitten by a spider, try to collect the spider whether alive and intact or dead and pulverized. This will help a trained arachnologist identify the offending arthropod and help direct the course of therapy. If you or your child is bitten by a black widow spider, seek medical attention immediately. Finally, despite its name, the black widow does not always eat her mate. In fact, in some species of widows the male brings food to his mate. What a guy!

References

Special thanks to courageous Dr. Shrewsbury who discovered and captured Lola, the gorgeous black widow spider featured in this episode. The great spider books ‘Biology of Spiders’ by Rainer Foelix, “Black widow spider” by Steve Jacobs, and the fact filled article “The Treatment of Black Widow Spider Envenomation with Antivenin Latrodectus mactans: A Case Series” by Steven R. Offerman, G. Patrick Daubert, and Richard F. Clark served as references for this episode.

Chemical engineers recycling forest matter in the DMV: Millipedes, Narceus americanus-annularis and Apheloria virginiensis

When disturbed, this beautiful millipede smells like almonds, but beware, it also releases other noxious compounds to defend itself. Image credit: Maggie Shuttlesworth

The arrival of scorching temperatures in the DMV provides an excellent reason to head for the hills for a cool hike. Forays to the Appalachian Trail and Catoctin Mountain Park in Maryland provide the perfect locations to escape summer’s heat and provide an opportunity to visit some of Mother Nature’s most interesting recyclers of organic compounds. Millipedes are detritivores, creatures that consume organic matter including mosses, algae, and decaying vegetation carpeting the forest floor. Millipedes belong to the subphylum of the arthropods called Myriapoda, those with “many feet”.

Do millipedes really snuggle?

 Do they really have a thousand feet? Nah, they don’t really have feet, but they do have legs and the record number of legs for a millipede is somewhere around 750. However, most millipedes have fewer than 400 legs. Young millipedes have only a few body segments, each of which bears a single pair of legs. As millipedes molt and grow, body segments with two pairs of legs each are added. Millipedes live two to seven years and can produce hundreds of offspring during their lifetime. Millipedes do not bite or sting, but several species secrete noxious chemicals from glands lining the margins of their body.

On a stony forest trail, we happened upon two remarkable members of the millipede clan. The first was Narceus americanus-annularis, one of the true giants of the millipede world in North America. Its otherwise dull brown body was accented with beet-red legs and red bands encircling the body at each segment. These colors might serve as a warning of noxious defenses ready to be unleashed by the millipede. Unable to resist handling Narceus earned me an acrid reward of benzoquinones, foul smelling droplets of the millipede’s chemical defense.

The many legs of the millipede work in a wavelike fashion to propel these timid grazers as they search for organic matter to eat. Watch as it munches moss on the surface of a boulder. Nearby, another millipede dashes across a forest trail. Bright contrasting colors may warn predators not to mess with these chemically defended detritivores. Defensive compounds released by this millipede smell like almond extract. You might not want to handle this one.

 A bit further down a trail, we encountered one of the flat-backed millipedes, perhaps Apheloria virginiensis. Blending in with the forest floor was clearly not this creature’s game as it sported lemon-yellow legs, alternating bands of yellow and black along the back, and pink-hewed margins. When plucked from ground, the smell of almonds filled the air and brought me back to my days of organic chemistry when benzaldehyde was the unknown compound on the lab practical. Benzaldehyde is the compound found in bitter almonds and is used as a flavoring in almond extract. Ah, but benzaldehyde is not the only compound found in Apheloria’s defensive secretion. The other more lethal moiety released by the millipede is hydrogen cyanide. Glad no one sniffed this millipede too deeply.

Curling into a defensive ball protects the tender underbelly of the millipede.

 Millipedes, important recyclers of organic matter, are well-protected by potent toxins and irritants that could make a bird, lizard, or toad think twice about messing around with these denizens of the forest floor. As temperatures soar into the 90s, consider taking a hike on one of the beautiful shady forests in the DMV and be on the lookout for busy millipedes, recyclers of organic materials. 

 Acknowledgements

 We thank the intrepid hikers of Maryland’s highlands, Erin, Ellie, Abby, Maggie, Jo, Paula, Laurie, and Kevin for providing inspiration for this episode. Thomas Eisner’s books “The Love of Insects” and “Secret Weapons” were used as resources for this story.

A rose by any other name would taste as sweet to sawflies: roseslug sawfly, Endelomyia aethiops, bristly roseslug, Cladius difformis, and curled rose sawfly, Allantus cinctus

It’s easy to see how the curled rose sawfly got its name.

On a recent visit to one of my favorite relatives, while enjoying the fragrances and beauty of roses in their garden, I noticed some unnerving injury to the foliage of several plants. The injury took the form of a type of herbivore mischief known as etching. Etching results when small insects use their jaws to remove soft tissues between the vascular bundles that crisscross leaves, leaving behind veins and a layer of epidermal tissue. This produces a windowpane, or skeletonized, effect, and these withered leaves often appear like someone took a blowtorch to them. A wide variety of beetles and caterpillars are the usual suspects when skeletonization is afoot. However, in this bed of roses, sawflies larvae were the culprits.

Not much left after the curled rose sawfly finishes a leaf. Can you see a second sawfly larva in this picture?

 Sawflies are unusual insects, an ancient branch of the bee and wasp clan. Unlike the larvae of bees and wasps that make their living consuming nectar and pollen or the flesh and blood of insects, the larvae of most sawflies are plant feeders. At first glance, sawfly larvae look like small caterpillars with slender bodies and distinct heads. Upon microscopic inspection, you can see that the posterior segments of the sawfly’s body bear small sucker-like appendages called prolegs. Prolegs adorn the abdominal segments of plant-eating moth and butterfly larvae as well. But moth and butterfly caterpillars never bear more than five pairs of prolegs. Most sawfly larvae have six or more pairs. Another difference between these look-alikes is the presence or absence of small fishhook-like structures called crochets on the prolegs. Caterpillars have them, sawfly larvae do not. Crochets help caterpillars hold onto the smooth surface of a plant leaf.

Dappled in sunshine, a pair of roseslug sawfly larvae strip nutritious tissue from a leaf blade, leaving only veins and a thin layer of epidermis behind. Through the lens of the microscope, you can get up close and personal with a bristly roselug as it gobbles leaf tissue. As leaves desiccate later in summer, they crinkle and turn brown as if toasted by a blowtorch.

 After spending the winter as juveniles in the soil beneath rose plants, in spring when foliage returns the roseslug sawfly completes its development, and small wasp-like adults fly to leaves where they deposit eggs with an egg-laying appendage called an ovipositor. The ovipositor has teeth like a saw’s blade, hence the name sawfly. Eggs hatch and the larvae proceed to pillage rose leaves through May and June. Fortunately, only one generation of these scalawags occurs each year, but in some years, they may be abundant enough that by the end of June they can make roses look like they have been assaulted by a flame thrower.

Impressive antennae adorn this tiny adult sawfly.

 In addition to skeletonization, several leaves had large chunks of leaf tissue missing from the edges of the blade. This defoliation was the handiwork of the curled rose sawfly, an insidious leaf-munching machine that is beautifully camouflaged. When not actively feeding along the margin of a rose leaf, it is curled on the underside of a leaf or on a bud where it blends in cryptically with plant. After several days of hide-and-go-eat, the entire leaf may be reduced to nothing but a mid-vein. When its development is complete, the larva bores into the twig, where it pupates. Later a small wasp will emerge, mate, lay eggs and initiate a second seasonal generation.

By mid-summer roses damaged by sawfly larvae look like they were toasted with a blowtorch.

 In May and June, I regularly inspect my roses for the telltale signs of skeletonization and defoliation. If sawflies are common enough to create problems for my roses, I simply squish the little buggers between my fingers or pluck them off and toss them in the lawn to become a feast for the ground beetles or lightning bug larvae lurking in the thatch. Several environmentally friendly insecticides listed by the Organic Materials Review Institute (OMRI) with active ingredients including insecticidal soap and spinosad work well against these sawflies. OMRI listed products are used for production of fruits and vegetables marketed as organic, and when insecticide applications are necessary, I try to select from the OMRI list whenever possible. As with all insecticides, always read the label carefully and follow precautions, including those safeguarding bees and other pollinators that might be on your roses. Strong directed streams of water are also reported to dislodge sawfly larvae from plants. If you have roses, be on the lookout for these rose-eating rascals. 

 References

 We thank Carole for providing the roses and sawflies that served as the inspiration for this episode. Two marvelous references, “Insects that feed on trees and shrubs” by W. T. Johnson and H. H. Lyon, and “Managing insects and mites on woody plants: An IPM approach” by J.A. Davidson and M. J. Raupp were consulted to prepare this episode.

Ground beetles to the rescue of caterpillar infested oak trees in the DMV: Calosoma wilcoxi and Calosoma scrutator

Calosoma wilcoxi (right) is about one third the size of its cousin, the fiery searcher Calosoma scrutator (left).

In last week’s episode, we met cankerworms pillaging hardwood forests on the western face of South Mountain in Maryland. A decade earlier, we witnessed a similar cankerworm outbreak further south on the mountain range at Weverton cliffs. During that eruption we arrived early enough in the predator – prey cycle to observe awesome Calosoma beetles putting a beat-down on cankerworm caterpillars, one of their favorite snacks. Let’s revisit that episode to learn about these fierce and marvelous predators. 

“While ogling fall cankerworms as they shredded leaves of maples and oaks, I was surprised to see many carabid ground beetles foraging in the canopies of trees. Now, as the name implies, ground beetles usually have their six tiny feet firmly planted on the ground where they provide great service hunting and eating a wide variety of soft-bodied pests, including rootworms, cutworms, and slugs, that plague our agricultural crops and backyard gardens. However, part of the clan, members of the genus Calosoma, are famous for their arboreal skills, ascending trees to deliver murder and mayhem to caterpillars.  

One of the largest members of Calosoma is a drop-dead gorgeous beetle that goes by the name the fiery searcher or caterpillar hunter. For an insect, it is big, often attaining a length of an inch and a half. My first encounter with the fiery searcher was disconcerting. Back in the days of Maryland’s gypsy moth plague, I lifted a burlap band on a tree to count gypsy moth caterpillars and out popped a fiery searcher that landed on my shirt. When I captured the assailant, it unleashed a potent chemical defense that lingered on my fingers for several hours. Calosoma beetles are notorious for producing potent defenses including methacrylic acid and salicylaldehyde.  

Despite their common name ground beetles, members of the genus Calosoma can be found hunting caterpillars in treetops. They are part of Mother Nature’s hit squad that helps to bring an end to important pests like cankerworms. There is murder and mayhem afoot in the tree canopy. Watch as this time-lapse video captures a Calosoma beetle using powerful jaws to crush and pulverize its cankerworm victim. This little cankerworm disappeared down the gullet of the beetle in less than five minutes. After finishing off one cankerworm, off it goes to find another. Arboreal ground beetles are awesome predators.

Although I did not see fiery searchers during my visit to cankerworm central, I was delighted to see scads of its smaller cousin Calosoma wilcoxi devouring cankerworms in the treetops and feasting on unlucky inchworms that had fallen on the ground. These beautiful hunters live two to three years or possibly longer. Romance happens in the month of June when mating pairs are active. Eggs are deposited in the soil in early summer, and they hatch in roughly a week. According to published accounts, larvae are ground dwellers where they consume a wide variety of prey, including gypsy moth and eastern tent caterpillars. Adult beetles hunt both day and night and in addition to fall cankerworms, on the menu are spring cankerworms, gypsy moth larvae, and eastern tent caterpillars.  

Several literature accounts associate the presence of Calosoma wilcoxi with the demise of cankerworms and the end of their devastating outbreaks in natural forest settings. One must wonder why some locations in Maryland, Virginia, and North Carolina have eruptions of cankerworms lasting years or even decades. One answer to this mystery may lie in the degradation of habitat that often accompanies the process of urbanization. In a recent review of responses of ground beetle communities to urbanization around the world, we discovered large forest dwelling ground beetles like our friend Calosoma wilcoxi to be the most severely impacted when forests become cities. Despite the presence of seemingly adequate prey for adults in some urban areas, other factors such as overwintering sites, food for larvae, cover for larvae and adults, and favorable thermal regimes may be inadequate or missing in developed areas. For our beleaguered oaks, maples, birches, and other hardwoods, let’s hope that Mother Nature’s hit squad of predators and parasites can bring the cankerworm catastrophe to a quick conclusion.” 

A quick conclusion to the cankerworm catastrophe is what we hope for. Unfortunately, history tells us that outbreaks of native caterpillars often last for several years in our natural forests. This year’s caterpillar outbreak, coupled with ongoing severe to extreme drought in parts of the DMV and extreme heat associated with El Niño this year, spell trouble for our native hardwoods. We will revisit South Mountain next spring to see how our oaks and maples fared. Fingers crossed the news will be good.      

To learn more about caterpillar outbreaks in the DMV this year please visit this link: https://news.maryland.gov/mda/press-release/2026/05/18/public-notice-maryland-department-of-agriculture-monitoring-frost-damage-and-caterpillar-outbreaks-in-western-maryland-hardwood-trees/

References 

Interesting accounts including “The genus Calosoma including studies of seasonal histories, habits, and economic importance of American species north of Mexico of several introduced species” by A. F. Burgess and C. W. Collins, “A meta-analysis of the effects of urbanization on ground beetle communities” by H. Martinson and M. Raupp, “Calosoma wilcoxi, A ground beetle” by T. Erwin, and “Defensive Secretions in Three Ground-Beetle Species (Insecta: Coleoptera: Carabidae)” by Sonja LečićSrećko, ĆurčićSrećko, and ĆurčićLjubodragVujisić,  were used to prepare this episode.