and Garden AGRICULTURAL MU Guide PUBLISHED BY MU EXTENSION, UNIVERSITY OF MISSOURI-COLUMBIA muextension.missouri.edu

Spiders Richard M. Houseman Department of Entomology

Spiders belong to the order Araneae of the class Arachnida. They are most closely related to scorpions, ticks and mites. Spiders have a body composed of two regions called the cephalothorax (head) and abdomen Pedipalps (body). They have eight legs, no antennae or wings, and an unsegmented abdomen. Four, six or eight eyes are located at the front of the cephalothorax. Also located Eyes Abdomen at the front of the cephalothorax are the pedipalps, appendages used for handling food (see Figure 1). Spinnerets are located on the posterior tip of the Cephalothorax abdomen. These structures are used to produce silk. Silk is used by spiders to make webs, construct egg sacs, line Figure 1. Characteristic form and structure of spiders. nests, wrap captured prey, or construct “balloons” with which to travel on air currents over large distances. regulating insect and other populations in More than 300 different spiders occur in Missouri. many different ecosystems. Spiders have a pair of Some of the more common groups include orb weavers, hollow, fanglike mouthparts and -producing crab spiders, jumping spiders and wolf spiders. These glands that they use to subdue their prey. They pierce groups are distinguished by the size and shape of their the exoskeleton and inject venom through their fangs bodies, the structure of the legs and other appendages, like a hypodermic needle. The venom typically para- and the size and relative position of the eyes. Tarantulas lyzes their prey. They also inject digestive juices that are not very abundant in Missouri but are occasionally break down the internal tissues. Later, they use their collected from the southern part of the state. The brown mouth like a drinking straw to suck out the body fluids. and black widow spider are the only two Not all spiders catch their prey in the same way. spiders in Missouri that are considered to be serious Some sit and wait on a web, while others leave their threats to human health. Most other species are consid- webs and actively stalk prey. Most spiders are active at ered nuisance pests when found in and around . night and usually remain hidden during the day. They Daddy longlegs will quickly run away when disturbed, unless they are (Figure 2) are not guarding an egg sac or young spiderlings. spiders but resem- Within a week after mating, females deposit eggs in ble them in shape a silken egg sac. The number of eggs deposited and the and number of number of egg sacs produced by a single female vary legs. They have according to species. It takes from a few weeks to a year segmented for the eggs to hatch and the young spiderlings to abdomens and Figure 2. Daddy longlegs. emerge. Young spiders typically climb to a high point only two eyes in their surroundings with suitable air currents, spin silk and do not produce silk. They are rarely found in the threads into the air and float away like tiny parachutists. living areas of a home. This behavior is called and aids in dispersal. Spiders generally live for only one or two years, but Spider biology and habits a few species can live as long as 5 to 20 years. Spiders All spiders are predators and should be considered grow by molting. This process consists of producing a beneficial in this role. They play an important role in new exoskeleton beneath the old one, splitting the old

$.50 G 7386 Printed on recycled paper exoskeleton and climbing out, enlarging the body, and during courtship and mating. hardening the new exoskeleton. The molting process Unlike most spiders, jumping spiders forage for occurs repeatedly throughout the immature stages, but prey during the day. Since they are active during the day, after reaching maturity, the vast majority of adult they are often noticed by humans. They do not use silk spiders do not molt. It is not unusual to see accumula- to make a web for capturing prey. Instead, they stalk tions of shed exoskeletons in undisturbed areas of their prey by approaching slowly to a short distance homes with large spider populations. before making a sudden leap onto it. They use silk as an anchor, attaching a strand before leaping. This allows Wolf spiders (Lycosidae) them to climb back to their original location if they miss There are many species of wolf spiders and they are the prey. widely distributed and common. They vary in size from medium to large, some species Crab spiders () measuring 2 to 3 inches in Crab spiders are distinctive in body shape (Figure diameter. Wolf spiders have 5). All of the legs extend sideways from the cephalotho- long, stout legs — the rax. The first two pairs fourth pair being the of legs are larger longest (Figure 3). The last than the last two, two pairs of legs have longer which gives hairs than the first two pairs. them a crablike Wolf spiders are found appearance. in a variety of habitats, They move about usually near moist by walking side- areas such as leaf litter, low- ways or backwards. growing vegetation, the Crab spiders do not edges of streams, ponds spin webs but capture Figure 3. Wolf spider. or rivers, and on sand- their prey by ambush. bars. They are known to Several species are brightly Figure 5. Crab spider. dig burrows or tunnel into natural cavities under colored and wait for their prey on objects. They actively stalk their prey during the night, flowers. They are known to catch a variety of flies and preying on ground-dwelling insects and other spiders. bees that come to flowers collecting pollen. Wolf spiders are known for their wandering habits, and it is not unusual to find some that have wandered Orb weavers (Araneidae) indoors. Orb weavers are often brightly colored with Female wolf spiders spin an egg sac attached to rounded abdomens, some with peculiarly angled their spinnerets. They are more aggressive when carry- humps or spines. However, there is considerable vari- ing an egg sac. When wolf spiderlings hatch, they crawl ation in size, color and shape in this group. They are onto the mother’s back and she carries them around for often recognized for beauti- a short period of time. The young of most wolf spiders ful, large, round webs, on which pass the winter half-grown and finish development they rest, head downward, wait- during the following summer. ing for prey. The webs consist of a number of radiating threads crossed Jumping spiders (Salticidae) by two spirals. The inner spiral Jumping spiders vary from begins in the center, winds outward, small to medium-sized with and is made of smooth threads like the stout bodies and short legs radiating threads. It covers only the 1 (Figure 4). The cephalothorax central ⁄3 of the web. The outer and abdomen are nearly spiral begins at the edges and equal in size. The body winds inward. It is made of is usually very hairy and more elastic, sticky threads, coated is often iridescent or brightly with a liquid substance. colored. They usually live in One of the largest and most the tops of low-growing commonly encountered members plants. Males often have of this group is Argiope aurantia, the Figure 6. Orb weaver. peculiar bunches of hairs or yellow garden spider (Figure 6). It may cover an area spots on their legs and head, 1.5–2.0 inches in diameter when at rest. The cephalotho- and they use these features to rax is silver and the oval abdomen has a yellow and attract the attention of females Figure 4. Jumping spider. black pattern. The legs are mostly black, blending to tan

Page 2 G 7386 at the bases. The web contains a large zigzag band radi- food. During the day they are resting in secluded places. ating out from the center. This spider feeds primarily on Other encounters occur when seldom-used clothes, grasshoppers and katydids. containing a spider that has been using the garment as a hiding place, are worn. Brown recluse spiders cannot Tarantula (Dugesiella hentzi) bite humans without some form of counterpressure. In Missouri, tarantulas are found only in the south- This pressure usually occurs when they are trapped ern part of the state. This large, hairy species is against the skin. uniformly choco- Both male and female brown recluse spiders are late brown with venomous. Human reactions to a brown recluse bite no noticeable vary considerably and depend on the amount of venom markings injected by the spider and the victim’s sensitivity to the (Figure 7). venom. A painful reaction can occur almost immedi- Tarantulas prefer ately, but often the victim won’t realize they have been drier areas, where bitten for an hour or more. Victims usually describe a they inhabit natural Figure 7. Tarantula. stinging sensation followed by intense pain. A small cavities or aban- white blister usually develops at the site of the bite. The doned burrows of other . They stalk crickets and affected area swells and becomes hard to the touch. This other large insects at night. The structure of their mouth- tissue dies and eventually sloughs away, leaving a parts is unique among spiders and requires them to sunken, ulcerated sore of various sizes. The typical reac- elevate their heads to insert their fanglike mouthparts tion has been described by physicians as unremarkable into prey. or mild and covers an area less than the size of a dime. Tarantulas are shy and avoid contact with humans. In a small percentage of cases (less than 5%) the sore However, when they are threatened and elevate their covers a larger area. heads, this posture is mistakenly interpreted as aggres- Medical attention should be obtained as soon as sive. Their venom is only slightly toxic to mammals, so possible after a bite occurs. Prompt medical attention the biggest threat is the puncture that would result from can prevent severe reactions and lessen the long-term their large fangs. effects. Healing takes place slowly, requiring six to eight weeks. Fatalities are rare. Brown recluse (Loxosceles reclusa) The name “brown recluse” describes the color and Black widow (Latrodectus mactans) habits of this spider. It is usually found in structures that The female black widow is jet black with a red hour- contain dry, cluttered glass-shaped marking on the space that is undis- underside of the abdomen (Figure turbed and has a 9). Some specimens have vari- supply of insects or ous other small red spots, other small organisms particularly on the top surface to serve as suitable of the abdomen. The abdomen is prey. One study found generally much larger than the this spider in about cephalothorax. Males are much 70 percent of homes smaller than females and usually that were sampled in have yellow and red bands and Missouri. spots over the body. Immature The color of the brown black widows have similar recluse varies from light tan markings. Only the to brown. They have six females are venomous. eyes and just behind their The black widow lives in eyes is a darker, broad, undisturbed locations under fiddle-shaped area that trash, litter, boards and rocks. Figure 9. Black widow. Figure 8. Brown recluse. extends to the back of the Little-used may be infested as well as crawl cephalothorax (head). The long neck of the fiddle points spaces, cellars and basements. These spiders construct 1 to the rear (Figure 8). A mature spider is about ⁄2 inch an irregular web in spaces between objects. They typi- 3 long by ⁄16 inch wide. The abdomen is generally not cally do not leave the web. Female black widow spiders much larger than the cephalothorax. With its legs in a are shy and nocturnal. Bites usually occur when humans normal standing position, the spider typically covers an come into direct contact with the web or when the spider area about the size of a quarter. is unknowingly pinned against their skin. Most encounters with brown recluse spiders occur The poison of the black widow spider affects at night when the spiders are active and foraging for nervous system function. The bite causes severe pain in

G 7386 Page 3 the vicinity of the bite, accompanied later by dizziness, a structure as free of clutter as possible by removing nausea, blurred vision and breathing difficulty. A physi- boxes, papers, clothing, lumber, etc. Periodically moving cian should be contacted immediately following a stored materials and vacuuming storage areas is suspected bite. When this happens, fatalities are rare and suggested. Minimize the amount of debris, firewood, recovery is usually quick and complete. landscape timbers, stones, etc. outside your home. Keep grass mowed and vegetation trimmed so that it does not Spider bites come into contact with the structure. People tend to fear spiders because they believe that Direct control: Clean away visible webbing, spiders spiders are aggressive and seek to bite humans. This is and egg sacs with a vacuum cleaner. Seal and dispose an unfounded fear. While it is true that spiders will rush of the vacuum bag immediately. Glue boards can be across their webs to investigate a vibration, this is just placed in areas of suspected spider activity, both to a natural hunting reaction to disturbance and should not monitor population size and to capture/remove be interpreted as aggressive behavior. Spiders do not unwanted spiders. Glue boards are very effective at attack and bite humans unless they are threatened or capturing ground-dwelling spiders like the brown provoked in some way. recluse or wolf spiders, but are not effective for spiders When a occurs, the victim is often that rest on their webs. unaware that it happened. Serious injuries or fatalities Chemical control: If you desire, appropriately labeled from spider bites are extremely rare. Very few spider pesticides may be applied inside the struc- species are considered to be a threat to human health, ture to areas where spiders rest. These areas include but the bite of the black widow or nooks and crannies in the basement, attic, closets, stor- can be serious. The reaction to a bite from these spiders age areas, etc. Indoors, it is best to direct chemical can range from mild to severe, depending on the indi- controls into hidden areas where the spiders are likely vidual that is bitten and the amount of venom injected. to be hiding, rather than indiscriminately applying The amount of venom injected varies from almost none chemicals to large, open areas. Dusts, wettable powders, to a full dose, depending on the quantity of venom in or microencapsulated formulations work best. Aerosols reserve at the time of , the length of time the fangs are not as effective unless they are applied directly to the are in the tissue and even the location of the bite. spider itself. If web-building spiders are the problem, Additionally, the reaction of different individuals to the you can treat the web and wait a few days before remov- same amount and type of venom will vary widely. ing the web. Outside, treat around doors and windows, under Spider management the eaves of the roof, under porches and in crawl spaces Prevention: Make sure buildings are in good physical if they are accessible. When homeowners are practicing condition. Good screening and sealing of cracks and good prevention and sanitation strategies, perimeter crevices will reduce the likelihood of spiders entering treatments by a professional pest management company your home. Yellow lighting near the exterior entrances can be helpful. These professionals are trained and to your home may also help to reduce the attractiveness licensed to use highly effective spider-control chemicals of these areas to spiders. that are not available to homeowners directly. However, Sanitation: Keeping areas in and around your home even these chemical barriers eventually break down, so free from debris and clutter is critical to spider manage- additional treatments would be needed to help ensure ment. If clutter exists, removing it is the first step to long-lasting spider control. reducing spider populations. Keep undisturbed areas of

■ Issued in furtherance of Cooperative Extension Work Acts of May 8 and June 30, 1914, in cooperation with the United States Department of OUTREACH & EXTENSION Agriculture. Ronald J. Turner, Director, Cooperative Extension, University of Missouri and Lincoln University, Columbia, MO 65211. ■ University UNIVERSITY OF MISSOURI Outreach and Extension does not discriminate on the basis of race, color, national origin, sex, religion, age, disability or status as a Vietnam COLUMBIA era veteran in employment or programs. ■ If you have special needs as addressed by the Americans with Disabilities Act and need this publication in an alternative format, write ADA Officer, Extension and Agricultural Information, 1-98 Agriculture Building, Columbia, MO 65211, or call (573) 882-7216. Reasonable efforts will be made to accommodate your special needs.

Page 4 G 7386 New 11/90, Revised 3/03/5M