Spiders in IllinoisSpiders in IllinoisStory and Photos ByHank Guarisco

diverse array of enemies or succumb-ing to harsh environmental conditions.Through time, the forces of naturalselection have led to the astoundingdiversity of spiders we see today.

Food HabitsWhether actively hunting their prey,

waiting in ambush among vegetation or

S

Characteristics all spiders share

include having eight jointed legs,

an exoskeleton and spinnerets at

the end of their abdomen.

Web-building spiders, such as the

common house spider, will eat their

old web, converting the protein into

new silk in as little as 30 minutes.

GoldenrodCrab SpiderGoldenrodCrab Spider

(Pho

toB

yJo

eM

cFar

land

.)

Spiders are a diverse andinteresting group of crea-tures found almost every-where in the state of Illinois.Their ubiquitous nature,ability to spin complex webs

and the habit of some species to fre-quent homes and gardens often alert usto their presence.

Currently, more than 630 differentspecies are known to inhabit the state.Spiders come in many shapes, sizesand colors and make their living in avariety of ways.

Any living organism can measuresuccess in life by thenumber of offspring ithas produced that growup to pass on theirgenes to future genera-tions. In order to dothis, a spider must gainenough energy to main-tain itself and to pro-duce a large number ofeggs, while avoidingdeath at the hands of a

CommonHouse Spider

CommonHouse Spider

14 / OutdoorIllinois November 2007

constructing intricate webs to ensnaretheir victims, spiders are consummatepredators. They are able to overcome awide variety of insects, arachnids andeven some vertebrates with the use ofsilk and their venomous bites. Althoughthe diet of the black and yellow gardenspider, Argiope aurantia, consistsmainly of insects, one individual cap-tured and consumed a skink. Membersof the hunting spider genus Dolomedesare commonly called “fishing spiders”because several species regularly eatsmall minnows and tadpoles. Beforeclosely approaching an ensnared,potentially dangerous prey item, webbuilders, such as the common housespider, Achaearanea tepidariorum,will securely wrap its intended victimwith silk, then deliver one or morebites once the prey is rendered immo-bile. Many years ago, I observed a largeblack and yellow garden spider which

had built a web in my college dormroom overcome a paper wasp (Polistessp.) that had become entangled in herweb. The wasp repeatedly attempted tosting the spider as she wrapped it insilk from a safe distance. Once it wasfully wrapped, she cut it out of her weband let it fall to the floor below.

Although they are predators, spidersare opportunists. Some wolf spidersand jumping spiders will readily scav-enge dead insects when they encounterthem. One researcher recently discov-ered that the brown recluse spider,Loxosceles reclusa, actually prefers dry,

dead insects over live ones. Some spi-ders occasionally feed on nectar andpollen as they actively wander over veg-etation in search of prey. Severalspecies have become more specialized.Pirate spiders (family Mimetidae) creepinto spider webs and pluck the silkstrands, mimicking the signals of preyor a potential mate. When the host spi-der approaches, it is immediatelyattacked by the pirate which delivers aparalyzing bite.

The small cobweb spiders in thegenus Argyrodes are called “klepopar-asites,” but actually make a liv-ing in several ways. They can buildtheir own cobwebs andcatch insects, they can live inthe webs of larger spidersand steal their food, or they can killand consume the host spider.

Avoiding PredatorsWhile going about the business of

life, spiders must avoid being eaten.One way to avoid predators, whichinclude birds, mammals, lizards,

Illinois spiders exhibit a range of

feeding habits. Fishing spiders (above)

can stay under water up to 40 minutes

to capture small minnows and tadpoles.

The diet of the black and yellow garden

spider is mostly insects.

November 2007 OutdoorIllinois / 15

A member of the pirate spider family,

longlegged sac spiders sneak into the

webs of other spiders to gain a meal.

Black and YellowGarden SpiderBlack and YellowGarden Spider

SixspottedFishing Spider

SixspottedFishing Spider

LongleggedSac SpiderLongleggedSac Spider

16 / OutdoorIllinois November 2007

amphibians, fish, insects and even otherspiders, is to blend into the backgroundor gain protection by resembling someformidable creature,such as an ant.

Although some ofthe colors, shapes andpatterns of spiders arequite striking, theirowners are virtuallyinvisible in their respec-tive habitats. One exam-ple is the white-bandedcrab spider, Mis-umenoides formosipes,which waits patientlyamong flower petals toambush insects thatcome to feed on nectar. The contrastingstripes of the diurnal zebra spider, Salti-cus scenicus, break up its outline as ithunts for insects on rocks. Wolf spiders(family Lycosidae), which are usuallyfound in leaf litter and on tree trunks,generally have a striped or mottledbrown coloration.

Several kinds of Illinois jumpingspiders (family Salticidae) gain protec-

tion by resembling ants. In addition tolooking like ants, these spiders runrapidly in the company of ants while

tapping the groundwith their first pair oflegs which are held inthe air like ant anten-nae. The imitation isgood enough to fooleven experienced spi-der collectors. Ofcourse, this defensemay backfire in thepresence of somejumping spiderswhich prefer to feedon ants. In this case,the ant-mimics often

are attacked more readily than otherspiders which did not resemble ants.

SensesWith the exception of jumping spi-

ders, which possess good vision, mostspiders rely mainly upon chemical, tac-tile and vibrational cues from their envi-ronment. There are long hairs (tri-chobothria) on spider legs which detectair movements. The legs also possessorgans that can sense different chemi-cals, such as pheromones, and slit-senseorgans that are sensitive to different fre-quencies of vibration. Web-builders usevibrational signals transmitted by theirwebs to discriminate among prey, ene-mies and potential mates.

The rear, middle pair of eyes of someground spiders (Gnaphosidae) candetect polarizedlight from the skywhich helps themorient in the land-scape as they huntduring twilighthours.

As visually ori-ented organismsourselves, wecan more easilyrelate to jumpingspiders, whichhave binocular vision and can see col-ors via a pair of large, frontally direct-ed eyes. Up to a distance of about 1foot, these spiders have the visualacuity of cats. So when Phidippus

audax, a jumping spider often foundin homes, turns toward you andseems to be watching you, it is notyour imagination!

Good vision also explains why manyjumping spiders are brightly colored.They engage in elaborate courtshipbehavior in which the males performstereotypic “dances” that display bright-ly colored parts of their anatomy to thefemale. In this way, jumping spiders arethe invertebrate equivalent to birds.These courtship displays enable malesand females of the same species to rec-ognize one another, and may evenrelate information concerning theirgood qualities as prospective mates.

To ensure reproductive success,many female spiders construct intricateegg sacs which they guard until theyoung are ready to disperse. Nursery-web spiders (family Pisauridae) carrythe egg sacs in their jaws until theyoung are about to emerge. At thistime, the mother places the egg sac inunderstory vegetation and constructsan elaborate, dome-shaped web aroundit, then stands guard. Spider eggs have ahost of insect predators and parasites,and protection by the mother increasesthe chances of her offspring’s survival.

Surviving WinterAnother challenge facing spiders in

Illinois is winter survival. Particularlybrutal winters can devastate popula-tions, so choosing a good hibernationsite is critical.

Many spiders pass the cold monthsas juveniles oradults. Jumpingspiders find shel-tered locationsout of the windand rain in whichto constructthick, silkenhibernacula.Rock crevicesand leaf litter canprovide good

winter retreats, especially if the latter isblanketed with a layer of snow. South-facing slopes which are exposed to thesun are ideal sites.

Spiders use a variety of techniques to avoid

predators, including coloration, patterning,

mimicking ants, and, in the case of jumping

spiders, jumping 20 times its own body length.

White-bandedCrab Spider

White-bandedCrab Spider

Bold JumperBold Jumper

Zebra JumperZebra Jumper

parachutes that their owners board tobe carried off with the wind. Balloon-ing spiders have been found up to10,000 feet high and many miles awayfrom land. This effective dispersalmechanism allows spiders to colonizeremote areas.

Some spiders construct webs tocapture prey. The typical orbweb con-sists of a framework attached to sup-porting objects, such as vegetation andtree limbs, radii which form thespokes of the wheel-like web, and thespiral which has sticky, drops of silkused to ensnare prey. The web’sowner can easily maneuver about, byclimbing on the framework and radiiwhich are not sticky.

Cobweb spiders, such as the com-mon house spider,the black widow(Latrodectus), andthe false widow(Steatoda triangu-losa), make a tangleweb with gluedroplets on the low-est silk strands whichanchor the web tothe ground. Shouldan ant wander intothe web, these strands are under ten-sion and snap and curl around theprey, suspending it in the web.

Other spider families produce addi-tional types of webs to catch prey,including sheetwebs, funnelwebs andhackle-bandwebs.

Because natural silk fibers are verystrong, recent attempts have beenmade to produce artificial silk.

Reason for ConcernAlthough spiders sometimes invoke

fear and loathing, only two species inIllinois are considered dangerous topeople. These are the black widow andthe brown recluse. A black widow biteis very painful, interferes with nerve

transmission, and occasionally causesdeath due to heart and lung failure.There is a very effective antivenin andrecovery is almost certain with propermedical treatment.

Most brown reclusebites cause local tissuedamage which healsafter several weeks ormonths. Sometimesthe damage becomesextensive and skingrafts are required.Antivenin is notpresently available forthis type of bite.

Of course, someindividuals may have an allergic reactionto any kind of foreign protein, and there-fore may react to the bites of harmlessspiders as well.

Aside from these few examples, spi-ders in Illinois are harmless, interestingcreatures that are interesting to observeand understand.

Hank Guarisco is adjunct curator ofarachnids at the Sternberg Museumof Natural History in Hays, Kansasand research associate of the FloridaState Collection of Arthropods inGainesville, Florida.

Most of the more than 600 spiders

found in the Prairie State do not bite

humans. Only bites of the brown recluse

(below) and black widow can be

considered dangerous.

November 2007 OutdoorIllinois / 17

Some spiders, including many orb-weavers such as the yellow and blackgarden spider, spend the winter insideegg sacs. Although they may be protect-ed from the cold due to physiologicalchanges that enable them to withstandfreezing temperatures, the spiderlingsin these egg sacs often fall victim tobirds which discover a ready wintermeal. In some areas, more than 98 per-cent of the egg sacs are torn open dur-ing the winter by birds.

Spinning SilkSilk is a fibrous protein that assumes

its final shape as it is pulled from thesilk-spinning organs (spinnerets) locat-ed at the rear end of the spider. As spi-ders move about in their environment,silk lines are played out and periodical-ly attached to objects. These functionin much the same manner as a moun-tain climber uses a rope to rappel downcliffs and to prevent accidental falls.

Silk also is used in the constructionof resting sacs and hibernacula. Underappropriate weather conditions, smallspiders let out silk which become small

Illinois Spiders

F or supplementing lessons aboutspiders, the DNR Division of Edu-

cation offers the Illinois Spiders posterfor teachers. Twenty-five types of spi-ders found in Illinois are depicted andinformation about their life historyalso is provided. Order this item atwww.idnrteachkids.com.

The Illinois Spiders poster wasmade possible in part by a grant fromthe Illinois Wildlife Preservation Fund.

Barn Funnel WeaverBarn Funnel Weaver

False WidowFalse Widow

BrownRecluseBrownRecluse