Fear-Busting Creepy Critters: Spiders
By Katy Gorsuch
“Bold Jumper” by Alex Andes-Gascon. Photo submitted to the 2019 DNR Photo Contest
Spiderwebs! Furry legs! The glint of multiple shining eyes!
It’s not difficult to see why spiders are so feared: they’re relatively small, possess an unsettling number of legs, and some are venomous to humans. They tend to lurk in dark and unused corners, which may contribute to our sense of alarm when we come into contact with them. But while avoiding harm and respecting animals’ personal space is always a good idea for the safety of both people and animals, understanding these “creepy” critters can give us a sense of appreciation for our native fauna.
Little, But Fierce
Nearly all species of spiders possess venom, with only the Uloboridae family of spiders and the Heptathela genus of trapdoor spiders possessing no venom glands at all, having lost them at some point in their evolutionary history. This being said, a majority of spiders’ venom does not affect humans in any tangible way, having been developed to hunt very different prey. Most spiders would have a significant amount of difficulty eating, let alone hunting, a human.
Of some 143 recluse spider species found globally, only 13 live in the US, 11 of which are native and two of which are introduced. Of these 13 species, nine are only found west of the Mississippi. The genus is a largely desert-based species, with only brown recluses (Loxosceles reclusa) being common east of the Mississippi River. Brown recluses are not native to Maryland nor any state which shares a border with Maryland, but they are occasionally found in the state due to transplanted individuals from western states.
Much more common in Maryland is the black widow. Five species of widow spider are found in the United States, but only two native and one introduced species occupy the state. The northern black widow (Latrodectus variolus) and the southern black widow (Latrodectus mactans) are native to the state, with the introduced species being the brown widow (Latrodectus geometricus). Despite their names, the northern and southern black widows heavily overlap throughout their respective ranges.
Notable about both the brown recluse and the three widows in the state is that all four venomous species are small spiders. All three widow species top out at about a half inch for the larger females, while brown recluses remain smaller than an inch long (about the size of a quarter). The males and juveniles are smaller, but often considered harmless as they cannot bite humans.
One of the best ways to identify a black widow is by their characteristic size and shape, but also by their luster. While the presence of their classic red hourglass on their abdomen is a sure tell that the spider is a black widow, many of us would prefer to not have to get so close to identify the individual! Black widows often have a luster and color that may make them look toy-like: one of the best ways to identify them is that they are shiny or glossy in a way that may make them appear plastic at first glance.
The introduced brown widow is a predator of the native black widow. Additionally, limited studies suggest venom from brown widows does not generally have the same impacts on humans as the venom of black widows.
A Blue Mud Wasp in Garrett County. Photo by Emilio Concari, via Maryland Biodiversity Project. Blue mud daubers preferentially prey on widow spiders.
Despite possessing a neurotoxic venom, black widows rarely bite humans. They prefer dark, undisturbed locations, and are often referred to as “shy” in comparison to other spiders. They are considered non-aggressive, and generally will not bite unless their web is disturbed or they are guarding eggs. Black widows will not always inject venom along with their bite (this is referred to as a “dry bite”). In fact, up to 15% of human bites may not have any venom at all. Even when envenomation occurs, venom does not necessarily mean severe complications. In an analysis of more than 20,000 cases, 65% were considered mild, while only 1.4% of cases were considered life threatening.This is not to say that black widow bites are harmless – companion animals like cats and dogs especially are at high risk for severe complications or death from a widow bite. If a bite is suspected, the patient should be taken to get medical assistance immediately.
So what is the best way to coexist with these native spiders? Avoiding areas where they may have taken up residence is an important part of avoiding bites, as well as keeping babies, children, and pets away from those areas. If you would like to introduce a more biological approach to black widow control in your own yard, golden alexander (Zizia aurea) is a native species which blue mud dauber wasps (who feed their children with many spider species) have shown preference for. While blue mud dauber larvae eat high-protein “spider snacks,” the adults themselves feed mostly on nectar flowers,so planting native plants in this class encourages the mud daubers to move in. In planting golden alexander, you also provide food for the larva of the black swallowtail (Papilio polyxenes).
Big and Bold
Some of the more readily seen spiders in Maryland are those that literally take up space!
Wolf spiders and fishing spiders are some of the more visible spiders we see and it’s not surprising we do – fishing spiders can grow up to 3.5 inches long! Over 100 species of fishing spider exist worldwide, with about eight present in the United States, and five in Maryland. The most commonly observed in Maryland by far is the dark fishing spider (Dolomedes tenebrosus).
Fishing Spider with Droplets by Angela Genito. Photo submitted to the 2023 DNR Photo Contest
Wolf spiders also tend to be more visible, with their size similar to fishing spiders, but with a shorter legspan. Both classifications tend to be large and fast, adaptations which help them hunt (rather than spinning a web and waiting for food to come to them). The traits which make them notable among the spiders unfortunately also lead to them startling the unsuspecting hiker or ambitious garage-organizer, but both are harmless in most circumstances and tend to be shy of humans. Despite their occasionally frightening appearance, hunting spiders like these may be welcome additions if you want to keep pest insects out of your home!
The newest member of the spider order in Maryland is the Joro spider (Trichonephila clavata), which has caused quite a stir with its large size and bright colors. While this arachnid looks intimidating, like many native spiders it is uninterested in biting people and when they do, their bites are no more impactful than the vast majority of spider bites. It remains to be seen how much impact the non-native Joro spider will have on the local ecosystem, having only recently moved into the state following over a decade of introduction to the southern United States. While any introduction of a new species can have catastrophic impacts on native species, the Joro spider has been observed preying on the brown marmorated stink bug (Halyomorpha halys), an invasive species that causes agricultural damage on a large scale.
Jorō Spider in Howard County, taken Sept. 15, 2024. Photo by Sean Maloney via iNaturalist (c) sean maloney, some rights reserved (CC BY-NC).
A Long-Legs to Stand On
A commonly repeated myth is that daddy longlegs are highly venomous and that only the fact that their fangs cannot penetrate human skin is the reason they are not considered dangerous. There are several issues with the statement, which may begin with identification of what species the common name applies to: both harvestmen (arachnids in the Opiliones order) and cellar spiders (Pholcidae family) are often called “daddy longlegs.”
Harvestmen do not have venom glands or fangs, but rather small grasping claws. While the cellar spider is capable of biting a human, they do not possess venom that could significantly harm a human.
Harvestmen have a wide number of defenses designed to escape predation by larger animals, including camouflage and mimicry, as well as freezing, fleeing, bobbing, chemical defenses, and self-amputating limbs in order to escape. Besides these wide and varied escape mechanisms, some species of harvestmen are also attentive parents, with paternal care of eggs evolving three separate times across the harvestmen family. Fathers tending to eggs will stave off predation by others as well as regularly cleaning the eggs. Cleaning is common to harvestmen as a whole- they are known to clean their legs after eating by drawing each one individually through their mouths, much as domesticated animals groom themselves.
Cellar spiders are no less interesting in their habits. Their webs have no adhesive the way most spiderwebs do, and instead rely on their unusual shapes to catch prey. When their webs are disrupted, some species are known to vibrate rapidly, sometimes moving into a circular pattern. This behavior may be designed to trap insects which have come in contact with their webs, or to confuse predators or make themselves harder to catch. Harvestmen may also bob in order to confuse predators and it has been proposed that the two arachnids may have parallel behavior in order to mimic each other. If their web continues to be disrupted, escape is the cellar spider’s next move, displaying the characteristic conflict-avoidance common across many spider species.
Very Demure, Very Mindful
Most spider species avoid people, and the species in Maryland are no exception to this. While spiders are common in forests, neighborhoods, and even homes, medically significant spider bites are rare. Of the “bugs” (terrestrial arachnids and insects) with which we interact most often, spiders are much less likely to bite humans unprovoked than many others. Often, spiders may share our homes without us seeing much of them at all. This seeming politeness may come from lack of interest or fear of us as roommates, but keeping our homes free from other bugs is an added benefit many of us cannot say about many human roommates.
Finally, and perhaps most importantly, you do not eat spiders while you sleep! This oft-repeated “fun fact” seems to have originated sometime around the end of the 20th century, but other than this we have very little information as to its origin.
However, spiders may eat other bugs while you sleep, and this is something both expected and welcome for many who have trouble sleeping when whining mosquitoes are trapped in their domicile.
For more about spiders, please read on:
A Brief Guide to Maryland Spiders
University of Maryland: Spiders in Maryland
Dancing, Deception and Cannibalism: The myths and realities of Maryland spiders
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