Spiders in the Home Fact Sheet No
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Spiders in the Home Fact Sheet No. 5.512 Insect Series|Home and Garden by F.B. Peairs, W.S. Cranshaw and P.E. Cushing* Spiders are beneficial arthropods, that Because spiders have a great ability to Quick Facts survive by feeding on insects. Oftentimes disperse, in addition to other factors that they are the most important biological affect their survival, the number of spiders • Spiders feed on insects and control of insect pests in gardens, fields, found in an area from one season to another other arthropods. This makes forests, and homes. However, their presence naturally varies. Also, spiders are able to them beneficial in helping is a cause of concern to some people. Many rapidly recolonize areas even if they have manage pests. people fear spiders because of stories or temporarily been eliminated. myths. Others object to spiders because of Most spiders in Colorado have a life cycle • Some spiders wander indoors their habit of building webs in and around that spans one year. However, widows and in the early fall when cooler the home. There are a few spiders whose bite some wolf spiders can live up to a few years, outdoor temperatures force requires medical attention. and tarantulas can survive a decade or more. them to find shelter. Spiders differ from insects in that they Adult male spiders are smaller than • Some spectacular spiders have eight legs (rather than six) and only two females, sometimes dramatically smaller. body regions (instead of three). The body Males are identified by the presence of are found in webs outdoors in regions include the cephalothorax (head and an enlarged pair of palps (front leg-like late summer, particularly the legs) and the abdomen. On the cephalothorax appendages ) which may appear somewhat banded argiope and the “cat- are usually six to eight eyes, often arranged in like miniature boxing gloves or a fifth pair face” spiders. two rows. The pattern of eye arrangement is of legs. The palps are used to transfer sperm. • Common spiders found characteristic for the different spider families. Male spiders are often more commonly found indoors include funnel web Some spiders capture prey by using in homes as they tend to wander during the silk and venom. Others are active hunters mating season in search of females. spiders, cobweb spiders, that ambush or capture prey. These spiders cellar spiders, and sac physically overpower their prey and then use spiders. venom to immobilize them. Common Colorado Spiders Funnel web spiders (Agelenidae) Life Cycle Funnel web spiders are the most common spiders found in homes, particularly during Females lay eggs in clusters of up to late summer and early fall. They produce several dozen. Most cover the eggs with a dense mats of silk in areas such as shrubs, sheet of tough silk that can attach to almost thick grass, or corners of buildings. A central any surface. The eggsac of many web- retreat (the base of the “funnel’) is usually spinning species are found in and around the used by the spider which then moves rapidly webs. Females of some species (wolf spiders, onto the web when prey enter onto it. cellar spiders, nurseryweb spiders) may carry Funnel web spiders are harmless but are the eggsac until the eggs hatch. often mistaken for the brown recluse, a spider Young spiders, known as spiderlings, whose venom is of medical importance, emerge from the eggsac and disperse. Many that does not naturally occur in Colorado. climb to the top of a nearby object, produce Funnel web spiders differ from the brown long filaments of silk (known as gossamer), recluse in that they have a darker brown and are carried by the wind. This method of color with black markings on the abdomen, dispersal is known as ballooning. Ballooning lack the characteristic “violin” marking on spiderlings can be carried long distances. the cephalothorax, have four pairs of eyes © Colorado State University instead of three, have striped legs, and are Extension. 9/02. Revised 9/13. *Colorado State University Extension entomologists considerably faster. www.ext.colostate.edu and professors, bioagricultural sciences and pest management; P. Cushing, curator of invertebrate zoology, Denver Museum of Nature and Science. 9/2013 Jumping spiders (Salticidae) disturbed, they characteristically bounce in Jumping spiders are active hunters. the web. Female cellar spiders carry eggs in They stalk and pounce on their prey rather her chelicerae (jaws) in a loose silk sac until than use silk to snare it. They are capable of they hatch. jumping several body lengths, possess large eyes, and the most common species are Yellow sac spiders (Miturgidae) brightly colored. As with almost all spiders, Sac spiders are active hunters. They get jumping spiders use silk to lay down a trail, their name because they spend daylight cover its eggs, and construct temporary hours in a flattened silken sac, typically shelters. located in the upper corners of rooms or Figure 1: Funnel web spider. in wall cracks. Most sac spiders are pale Dysdera crocata (Wood Louse Hunter) colored. They are usually the most common “Roly-poly Hunter” spider found wandering in homes during This smooth bodied spider is perhaps fall, particularly at night. Cheiracanthium best distinguished by its large fangs which species are suspected as being the most it uses to feed on pillbugs (roly-polies) and common source of spider bites in homes. other hard-bodied prey. When full grown The bite, although painful, usually causes they are about .5 inch in length. Dysdera no other symptoms and the pain subsides have a generally creamy gray body with after a few minutes. distinctly reddish legs and cephalothorax. They live in a silk retreat and hunt at night. Wolf spiders (Lycosidae) Their bite can be painful but they are not Wolf spiders are active hunters that do Figure 2: Funnel web spider. aggressive and their venom is not known to not produce a prey capture web. They may cause medical problems. make a silk lined retreat in soil, under rocks or in other protected sites. Most are grey or Ground spiders (Gnaphosidae) brown and some are quite large including Ground spiders, as their common name the giant wolf spider (Hogna carolinensis) implies, are most often found under rocks and some burrowing wolf spiders or logs where they build silken retreats and (Geolycosa spp.) which are commonly emerge only to hunt. Some species wander mistaken for tarantulas. Smaller species indoors when the weather turns cold. somewhat resemble funnel web spiders. Ground spiders are harmless to humans. An unusual habit of wolf spiders is that the female carries the egg sac attached to her spinnerets. The newly hatched young Figure 3: Ground Spider. Cobweb spiders/Comb footed spiders (Theridiidae) crawl on the female’s back for the first few weeks of life. Cobweb spiders are common Wolf spiders occasionally enter homes, inhabitants of dark corners around the particularly in areas of new development home. They have a generally bulbous body where their habitat was disturbed. They and create messy webs with sticky threads. are normally shy and not dangerous to The majority of these spiders are harmless, humans, although large species can bite. although one group, the widow spiders in the genus Latrodectus, are potentially Araneus spiders (Araneidae) dangerous. The family also includes spiders in the genus Steatoda that are also generally Several orb weaving spiders of the genus black and sometimes mistaken for widow Araneus are commonly found outdoors late in the season. They are usually brownish in Figure 4: Jumping spider. spiders, but they have a large white band around the front of the abdomen and lack color with a large and prominent abdomen the orange-red hourglass pattern on the that is dimpled and marked. Some species, underside of the abdomen. known as “barn” or “garden” spiders, make geometric webs among vegetation, Cellar spiders (Pholcidae) buildings, windows, or outdoor lighting. The largest and most commonly Cellar spiders are usually found in dark observed species is the “catfaced” or corners of cellars, crawl spaces, and garages. “monkeyface” spider, Araneus gemmoides. They are very long-legged and often Large females may be almost 1 inch in confused with daddy-long-legs. However, diameter and are generally round with they are true spiders that spin untidy webs a prominent pair of humps on the back. which are often quite extensive. When Araneus spiders are harmless. Figure 5: Jumping spider. Banded Garden spider (Araneidae) contain a nerve venom. Fortunately, widow The largest and most striking of the orb spiders are non-aggressive and rarely bite. weaving spiders found in Colorado is the When bites do occur they happen when the banded garden spider (Argiope trifasciata). female is provoked, for example, when an It is found in late summer and early fall unwitting person presses down on a spider among shrubbery and in gardens where that is resting beneath a log or rock. See they make a highly symmetrical orb web. fact sheet 5.605, Western Widow Spider for Females are generally silvery, with dark and additional information. yellow striping. Males are rarely observed and are much smaller than the females. The Brown Recluse spider Figure 6: Cob web spider. banded garden spider is harmless. The brown recluse (Loxoceles reclusa) is rare in Colorado because of our cold Tarantulas (Theraphosidae) winters and dry climate. However, it is Tarantulas are found in southeastern common to areas along the southern and southwestern Colorado. Mature male Mississippi Valley and are occasionally spiders are commonly observed when they brought into the state but rarely, if ever, wander across roads in late summer in get established. The brown recluse lives search of females. Tarantulas are among within a loose, messy web in dark corners the longest lived of all spiders.