Spiders are some of the hardest working wildlife in Maryland. Many
people are fearful of spiders and often overlook the critical role
they play controlling insect pests. Knowing how to distinguish some
of the different types of spiders and understanding the important
functions that they serve in our environment can often lead to a
greater appreciation of their beneficial qualities. This online
guide is not an inclusive list of spiders found in Maryland, but it
contains many commonly encountered spiders. There are over 40,700
species of spiders worldwide and hundreds of species in Maryland.
What it Takes to be a Spider
Spiders are classified as Arachnids. Other types of Arachnids
include mites, ticks and harvestmen (aka “Daddy long-legs"). Spiders
are different from other Arachnids because their body is divided
into two major sections which are separated by a pedicel or
narrow connection. The front part of the spider’s body is called the cephalothorax while the back is called the abdomen.
Attached to the abdomen are finger-like appendages known as
spinnerets. These structures are the silk-spinning organs and
are often used for spider identification.
Super Silk
All spiders spin silk, but not all spiders use the silk for their
webs. Some spiders use the silk to protect their eggs, store their
food or build a temporary home. Spider silk is strong and elastic
which allows them to catch fast flying food or secure their young to
their backs. On a per weight basis, spider silk is stronger than
steel!
Venom and Bites
Many of the spiders in Maryland
possess venom, but the black widow is the only native Maryland
spider that is dangerous to people. All other venomous Maryland
spiders either have too little venom to affect people or their venom
is specially adapted for their prey.
Brown recluse spiders are
not native to Maryland, but on very rare instances they can stow
away on packages from the Midwest and the Southwest where the Brown
recluses are more common.
Only 10% of Brown recluse bites
develop into tissue necrosis (cell death) around the bite area.
Recently, many researchers are realizing that many previously
diagnosed brown recluse bites were actually methicillin-resistant
Staphylococcus aureus, or MRSA infections. Treatment for MRSA
infections and spider bites are similar.
Brown recluses can be identified by several characteristics such as: 1) six eyes arranged in pairs, 2) a dark violin-shape on the cephalothorax (head), 3) uniformly light-colored legs (without stripes or bands), 4) 3/8 inch length body and 5) no spines on the legs. Brown recluses are often misidentified. The University of California has an excellent page on brown recluse identification and misidentification here.
Spider bites are actually quite uncommon, and most spiders will only
bite humans in self defense. While spiders have fangs, they are
usually too small to leave visible puncture wounds. Many times,
spider bites will result in pain, redness, itching and swelling that
lasts a couple of days. Spiders rarely bite more than once, so
multiple bites are usually caused by insects such as fleas, bedbugs,
chiggers, ticks, mites and biting flies.
Although black widow and brown recluse spider bites are rare, care
must be taken to properly identify and treat the wound. Healthy
adults may only experience mild symptoms but children, the elderly
and those with compromised immune systems should be extra cautious.
Guide to Common Spider Groups
Cellar spiders
Family: Pholcidae
Cellar spiders tend to have extremely long, skinny legs with small
bodies. Cellar spiders make stringy webs, often in the corner of
rooms, to catch flies and gnats. When food is scarce, Cellar spiders
will abandon their webs and tap on another spider’s web to mimic
captured prey. When the other spider comes out to investigate its
“catch”, the cellar spider will eat the unsuspecting spider. Cellar
spiders are commonly found in homes, but they typically stay in one
place and don't bother people. Cellar spiders are not known to bite
people.
Cobweb spiders
amily: Theridiidae
Black widows
(Latrodectus)
Black widows are distinctive spiders. The females are shiny black
with a red hourglass on the bottom of her abdomen while males have a
more vibrant pattern on their abdomen consisting of many red and
white spots. Male black widow spiders are rarely encountered and are
not known to bite humans.
Black widow bites feel like a minor pinprick, but dull pains will
soon develop in the area of the bite. The affected area will
generally begin to cramp and other symptoms such as sweating, nausea
and vomiting may occur.
Black widow spiders are cobweb spiders that spend most of their time
in their webs. Black widows tend to make their webs in undisturbed,
uncluttered areas on porches and in sheds. To discourage them from
inhabiting an area, then knock down their webs with a broom or a
high pressure hose. In some areas, you can vacuum up spiders and
their eggs, but be sure to immediately place the vacuum cleaner bag
in a plastic bag, seal tightly, and discard in a container outdoors
as this prevents captured spiders from escaping into the home.
Common house spider
(Parasteatoda tepidariorum)
True to their name, common house spiders are frequently found in
human dwellings. Like Black widows and other cobweb spiders, common
house spiders build messy, tangle webs usually around windows.
Common house spiders can have variable appearances. Females are
generally mottled gray or tan while the males tend to have a more
reddish appearance.
Crab spiders
Family: Thomisidae
Crab spiders are not active hunters and use the art of camouflage to
snag their prey. Crab spiders are named after their crab-like
appearance with large front legs that are often held out to the
sides of their body. These spiders come in all different colors,
many of which are specially adapted to their hunting grounds. For
example, the goldenrod crab spider is a bright yellow color which
allows it to easily blend in with the yellow petals of goldenrods.
Crab spiders are viewed as beneficial to people as they tend to eat
many insect pests found in gardens and flower beds. Interestingly
enough, scientists believe that the venom of many crab spiders is
more potent than most spiders. This allows the crab spiders to
quickly subdue prey such as bees. Crab spiders are not known to bite
humans, though.
Funnel weavers/Grass spiders
Family: Agelenidae
Funnel weaving spiders look very similar to Wolf spiders, but they
make webs and have three rows of eyes. True to their name, funnel
weavers make funnel-like webs along the ground in which the spider
hides in. When a prey species crosses the web and vibrates it, the
spider will jump out and grab its new meal. Because of this feeding
strategy, funnel weaving spiders are designed to be incredibly quick
and most rarely leave their webs.
Jumping spiders
Family: Salticidae
Jumping spiders are truly the Casanovas of the Arachnid world. Not
only are many jumping spiders brightly colored, but the males put on
elaborate songs and dances for the ladies. Jumping spiders are named
for their movements which consist of jumps or short, rapid runs.
Jumping spiders tend to have a large pair of eyes mounted on the
front of a relatively flat-face. The other three pairs of eyes are
relatively small in comparison.
Jumping spiders are adept hunters. Their keen eyesight paired with
speed allows them to catch prey with amazing accuracy. Jumping
spiders do not build webs, but they do use their silk as a tether
when they go to pounce on prey. If their aim is off, they can use
their silk thread to return to their original location. Jumping
spiders are often found in and around human structures, especially
in barns and sheds.
Nursery web and Fishing spiders
Family: Pisauridae
Nursery web spider
(Pisaurina spp.)
Nursery web spiders are large, hairy spiders that usually have a
dark stripe running through their eyes down the back of them.
Nursery web spiders consist of several species in the genus
Pisaurina. Nursery web spiders will carry their egg sacs in their
jaws and then will build a “nursery tent” shortly before they hatch.
The female will guard the nursery web until the young spiders reach
their first molt.
Most adults get up to an inch in size. Nursery web spiders can
commonly be found in and around homes, but they pose little to no
threat to humans.
Fishing spiders
(Dolomedes spp.)
Fishing spiders look very similar to wolf spiders in regards to size
and coloration. However, fishing spiders tend to have much longer
legs, relative to the rest of their bodies and have alternating
brown/black bands on their legs. Many species of fishing spiders
live near water and often catch small fish, aquatic insects and
tadpoles. One exception is the dark fishing spider (Dolomedes
tenebrosus) which lives in wooded areas and occasionally seeks
refuge in basements.
Orb-weavers
Family: Araneidae
Orb-weavers strongly resemble cobweb spiders. However, true to their
name, orb weavers create webs that are organized and have a circular
grid. Orb-weavers need structures such as weeds, fences, trees,
walls or other upright structures to build their webs. Orb weavers
are considered beneficial to humans as they eat many pest insects
including the invasive Brown-marmorated stinkbug!
Black and yellow garden spider
(Argiope aurantia)
True to its name, the black and yellow garden spider is often seen
n and around gardens. These spiders are orb-weavers, meaning that
they spin their webs in a circle or an orb. These webs can be up to
2 feet across, while the spiders themselves can have a leg span of
nearly 2.5 inches! Females are much larger than the males, and often
times, these spiders will decorate their web with a zig-zag of white
silk. Black and yellow garden spiders prefer to build their webs in
sunny areas and often will rebuild their webs every day.
Micrathena spiders
Spiders in the genus Micrathena tend to have spiky abdomens and are
notorious for weaving webs at face level along trails. If you have
ever run into a spider’s web in late summer while hiking in
Maryland, then there is a good chance it was a Micrathena web!
Micrathena spiders feed mostly on small flies, gnats and mosquitoes.
Males do not build webs, rather they let the ladies do all the work.
When a male is ready to mate, he will weave a ‘mating thread’ into
her web before mating with her. Many times, females will kill the
males shortly after mating. Spined Micrathena spiders (Micrathena
gracilis) are the most common Micrathena in Maryland.
Marbled orb weavers
(Araneus marmoreus)
Marbled orb weavers are some of the showiest spiders found in our
area. The abdomens of these spiders become yellow with black marbled
patterns as they mature, and sometimes around Halloween, the yellow
turns to an orange color. Most marbled orb weavers hide in rolled up
leaves until an unsuspecting prey gets captured in their webs.
Wolf spiders
Family: Lycosidae
Wolf spiders are agile hunters that live alone and actively hunt
prey instead of tending to webs. Wolf spiders have exceptional
eyesight and often hunt at night. Their eyes are reflective, so they
can often be seen at night by shining a flashlight over them. Wolf
spiders tend to be brownish-gray and can grow just over an inch in
length. Wolf spiders are often confused with the Brown recluse, but
they lack the unmistakable violin-shaped marking behind the head.
Female wolf spiders are very maternal and will carry their eggs in a
sac on their back. When the eggs hatch, the female will carry the
hatchlings on her back until they are large enough to hunt on their
own. Wolf spiders are not aggressive, and like most spiders, will
only bite when they feel threatened.
Invite Wildlife to Your Backyard!
For Additional Information, Contact:
Kerry Wixted
Wildlife and Heritage Service
580 Taylor Ave, E-1
Annapolis, MD 21401
kerry.wixted@maryland.gov
Phone: 410-260-8566
Fax: 410-260-8596
Acknowledgements:
- Cellar spider, photo by Olaf Leillinger
-
Black widow spider, photo © Richard Schuerger
-
Common house spider, photo © Richard Schuerger
- Crab spiders on thistle, photo by R.H. Wiegand
-
Funnel weaver, photo © Richard Schuerger
-
Jumping spider photo © Richard Schuerger
- Nursery web spider, photo by Kerry Wixted
- Fishing spider, photo by Richard Orr
- Black and yellow garden spider, photo by Kerry
Wixted
- Spined Micrathena spider, photo by Patrick Coin
- Marbled orb weaver, photo by Kerry Wixted
- Female Wolf spider, photo by Kerry Wixted
- Wolf spider, photo by Richard Orr
- Brown recluse spider, photo by Mark Dreiling