7A Ch13 Cheat Sheet: Spiders

🎯 Top 5 Traps

1

Brown recluse bite is NOT initially painful — sharp but no immediate pain. Black widow bite IS immediately painful. The pain timeline is opposite. BLACK WIDOW: bite is immediately painful with 2 small red fang marks; pain increases over the first half-hour; followed by headache, dizziness, shortness of breath, abdominal/back pain. BROWN RECLUSE: sharp but not painful at the bite; a blister is quickly raised, broken, surrounded by a red welt; depressed center turns dark within a day; dead tissue sloughs away; scars over in 1 to 8 weeks.

2

The brown recluse FIDDLE mark is on the CEPHALOTHORAX — NOT the abdomen. The broad base of the fiddle begins at the eyes, the narrow fiddle neck ends just above the attachment of the abdomen. The abdomen is uniformly tan to brown with NO markings. Common reverse-error: looking on the abdomen for the fiddle. Legs are long; the second pair is longer than the first.

3

A necrotic lesion alone does NOT confirm a brown recluse bite — other biting arthropods produce similar lesions. The chapter is explicit. Always KILL the spider and take it to the physician with the victim for positive identification. The spider is delicate and often found lying where it was slapped by the victim. Death seldom occurs but the bite is debilitating and psychologically traumatic.

4

Yellow house spider webs in GAS APPLIANCE JETS AND BURNER TRAINS can interfere with gas flow. Look for webs in inactive gas appliances during the summer-winter transition: gas stoves, gas refrigerators in recreational vehicles, gas air conditioners, and through-the-wall gas furnaces. The silken obstructions interfere with gas flow; OPERATIONAL FAILURE of these appliances can indicate yellow house spider presence.

5

Black widow control requires the pesticide to DIRECTLY CONTACT the spider — they do not leave their webs or wander after establishment in the summer. Residual barrier treatments will not reach them. Move cautiously when treating any potential spider harborage (stacked pots/baskets, firewood piles, rodent burrows, water meters, stacked boards, under bricks/stones). Mud dauber wasps (Ch.12) are a natural biological control — they paralyze spiders for their larvae.

🔢 Numbers You Must Know

Number

What It Represents

3,000

Kinds of spiders in the United States — order Araneae, class Arachnida

4 pairs of legs

All spiders have 8 legs (4 pairs) attached to the cephalothorax — like all arachnids, NO antennae

2 body regions

Cephalothorax (head + thorax fused; eyes, mouthparts, legs) + abdomen (saclike, with spinnerets near the end)

1/2 inch or larger

Black widow female body size — shiny black with red hourglass

1/4 inch

Yellow house spider length — legs and cephalothorax darker than abdomen; yellow, white, or greenish

Up to 1/2 inch

Jumping spider length — husky cephalothoraxes, brightly colored (sometimes iridescent)

About 1 inch

Large orb weaver body length, with very long legs; web spans about 1 foot across

Half-hour

Time period over which black widow bite pain increases at the bite site before secondary symptoms set in

Dime to quarter

Size of brown recluse bite lesion (raised red circle with depressed dark center)

1 to 8 weeks

Brown recluse bite scarring time — dead tissue sloughs away then scars over

1 to 2 weeks

Brown recluse retreatment interval — monitor and retreat if indicated

Late 1940s

Yellow house spider (Chirocanthium mildei) introduction date into the United States

🔀 Easily Confused

Pair / Group

Distinguishing Feature

Spider vs Insect

Spider (Arachnida): 4 pairs of legs (8); 2 body regions (cephalothorax + abdomen); NO antennae; chelicerae (fangs) instead of typical mouthparts. Insect (Insecta): 3 pairs of legs (6); 3 body regions (head + thorax + abdomen); 1 pair of antennae; usually wings.

Black widow vs Northern widow

Both have round shiny black abdomen, hang upside down, weave coarse silk webs. Black widow (Latrodectus mactans): RED hourglass on belly; eastern and southern US. Northern widow (L. variolus): YELLOW TO WHITE hourglass; native Michigan species; common around pine stumps.

Black widow vs Brown recluse

Two dangerous US spiders. Black widow: 1/2 inch or larger; ROUND shiny black abdomen with RED HOURGLASS on belly; hangs upside down in coarse-silk tangled web; bite IMMEDIATELY painful. Brown recluse: smaller; OVAL tan-brown abdomen with NO marking; FIDDLE mark on CEPHALOTHORAX; fine irregular web; bite NOT initially painful but ulcerates over hours.

Brown recluse vs Yellow house spider

Both can cause tissue lesions. Brown recluse: causes severe necrotic lesion 1-8 weeks; concentrated in central US; oval tan body with fiddle on cephalothorax. Yellow house spider: less severe tissue deadening; LARGE MARGIN OF SAFETY (cannot pierce everyone's skin); 1/4 inch; weaves PROTECTIVE WHITE SILKEN COCOON-LIKE WEBS to overwinter and molt.

Cobweb spider vs Black widow

Both have GLOBULAR abdomen and weave irregular webs. Cobweb spider: smaller; abdomen always DULL color (not eye-catching); harmless. Black widow: 1/2 inch or larger; SHINY black; RED HOURGLASS. Black widow is technically one of the cobweb spiders.

Orb weaver vs Cobweb spider web

Orb weaver: large flat web ~1 foot across with many straight strands radiating + spiral threads; on porches, trees, shrubs; outdoors. Cobweb spider: small irregular webs; characteristically in upper inside corners of window frames; indoors.

Wandering vs Web-weaving spiders

Wandering: hunt by stalking/ambush — wolf, jumping, crab spiders. Web-weaving: catch prey in webs — orb weavers, cobweb spiders, black widow. Wandering spider control = exclusion + direct contact (pesticide must contact spider directly).

Wolf vs Jumping vs Crab spider

Wolf: hairy, fleet, common under leaf litter/rocks/logs; ground floor, dim light; painful but not dangerous bite. Jumping: small (up to 1/2 inch); brightly colored, sometimes iridescent; husky cephalothorax; QUICK RUSHES, JERKS, JUMPS; common at windows. Crab: legs extend out to sides, scuttle CRAB-LIKE; hide in flower blossoms; may change color to match flower; arrive in cut flowers.

Boathouse spider problem vs Monument spider problem

Same root cause: lights attract midges, midges feed spiders, spiders defecate spots that are difficult to remove (boathouses: pleasure boat decks; monuments: limestone/marble). Both: pesticide NOT effective — manipulate LIGHTING to control food source. Boathouses additionally use fans (flies/gnats don't rest in breezy areas).

🕷️ Spider Species ID Quick Reference

Species

ID / Size

Habitat / Behavior

Black widow
Latrodectus mactans

Female: 1/2 in or larger; large round shiny BLACK abdomen with RED HOURGLASS (touching triangles) on belly. Male: small, white, streaked yellow + red — NOT dangerous.

Eastern + southern US. Hangs UPSIDE DOWN in tangled coarse-silk web. Stacked pots/baskets, firewood piles, rodent burrows, water meters, under bricks/stones, crawl spaces, porches, garages, sheds. Females not aggressive but defend web.

Northern widow
L. variolus

Same as black widow EXCEPT hourglass is YELLOW TO WHITE rather than red.

Native Michigan species. Common around pine stumps.

Brown recluse
Loxosceles reclusa

Smaller than black widow. Dusky tan or brown; OVAL abdomen, uniformly tan-brown, NO markings. Dark FIDDLE/violin mark on CEPHALOTHORAX (broad base at eyes, narrow neck above abdomen). Long legs; 2nd pair longer than 1st.

Range: central Texas N to Iowa, S through IL, NC/SC, NW Georgia/Alabama. Common in older homes in Midwest. Indoors in northern range. Avoids high-traffic areas; closed/unused rooms; stored clothing. Wanders in evening. Fine irregular web.

Yellow house spider
Chirocanthium mildei

About 1/4 in. Legs and cephalothorax DARKER than abdomen. Yellow, white, or greenish.

Introduced US late 1940s. Migrates into structures + automobiles late summer/early fall. Weaves PROTECTIVE WHITE SILKEN COCOON-LIKE WEBS to overwinter and molt to adult in spring. Webs in GAS APPLIANCE JETS interfere with gas flow.

Orb-weaving spiders

Large + conspicuous (orange/yellow or black/yellow); body about 1 in long, very long legs.

Several hundred US species. Webs ~1 foot across with straight radiating strands + spiral threads, on porches/trees/shrubs. Sit in center waiting for flying insects. NOT aggressive — webs can be knocked down. Includes the barn spider ("Charlotte" of Charlotte's Web).

Cobweb spiders

Small; same globular abdomen shape as black widow but DULL in color.

Many species; black widow is one of them. Small irregular webs in upper inside corners of window frames. Defecate spots that discolor painted wooden trim — difficult to remove. Regular dusting eliminates problem.

Wolf spider

Hairy, fleet — large enough to frighten people.

Common outdoors under leaf litter, rocks, logs. Indoors: stay on GROUND FLOOR, active in dim light. Painful bite if handled but NOT dangerous.

Jumping spider

Up to 1/2 in. Husky cephalothorax; brightly colored (sometimes iridescent).

Active during DAY. Common around windows; feed on light-attracted insects. Hold front legs UP IN FRONT when approached. Move in QUICK RUSHES, JERKS, or JUMPS. Enter from shrubs near windows or on plant blossoms.

Crab spider

Small; dark or tan or brightly colored orange/yellow/cream. Legs extend out from sides — SCUTTLE CRAB-LIKE.

Hide in FLOWER BLOSSOMS and ambush insects. Some change color to match flower. Often brought inside in CUT FLOWERS — abandon when food unavailable. Pests wherever flowers are introduced.

⚠️ Dangerous/Biting Spider Comparison

Feature

Black Widow

Brown Recluse

Body shape

1/2 in or larger; ROUND shiny black abdomen

Smaller than black widow; OVAL tan-brown abdomen

Distinguishing mark

RED HOURGLASS on belly (touching triangles)

Dark FIDDLE/violin on CEPHALOTHORAX (NOT abdomen)

Web type

Tangled web of coarse silk in dark quiet locations

Fine irregular web in unused/closed rooms

Bite pain timing

IMMEDIATELY painful at bite; pain increases first half-hour

Sharp but NOT initially painful; lesion develops over hours

Bite signs

2 small red fang marks at bite site

Blister raised + broken; red welt; depressed center turns dark within a day; size dime to quarter

Secondary symptoms

After half-hour: headache, dizziness, shortness of breath, abdominal/back pain

Dead tissue sloughs away; scars over 1-8 weeks; debilitating + psychologically traumatic

Treatment recommendation

Hospital treatment ASAP; especially for children/elderly

KILL spider, take to physician for ID; other arthropods produce similar lesions

Pesticide approach

Must DIRECTLY CONTACT spider — does not leave web or wander after summer

Residual in cracks/crevices outside daily traffic patterns; spot treatments LESS effective (spider only contacts with leg-tip hairs)

Yellow house spider (for context): Bites if pressed or confined (e.g., during sleep). Causes pain and reddening at the bite; some tissue deadening but MUCH less severe than brown recluse. Has a LARGE MARGIN OF SAFETY — cannot pierce everyone's skin. Children showing 2 fang marks may have been bitten by this spider.

💡 Memory Hooks

Hourglass vs Fiddle: "Black widow wears the hourglass on her belly; brown recluse wears the fiddle on his back." Two ID anchors, two body locations.

Pain timeline: "Black widow stings now; recluse waits and ulcerates." Black widow = immediate pain; brown recluse = delayed lesion.

Arachnid signature: "Eight legs, two body parts, no antennae." Quick spider-vs-insect ID.

Yellow house surprise: "Yellow house webs in gas appliances." Operational failure of stoves, RV refrigerators, and through-the-wall furnaces in fall = yellow house spider clue.

Fiddle location: "Fiddle BASE at the eyes, neck above the abdomen." On the cephalothorax — never on the abdomen.

Black widow contact rule: "Black widows don't wander — touch the spider with your spray." Residual barriers won't reach them.

Boathouse + monument: "Lights attract midges, midges feed spiders, spiders stain everything." Same problem, same solution: control the lights.