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What do they look like?

Sac spiders are medium sized (5-12 mm body length) pale spiders. Like all spiders they have two body-segments, a cephalothorax in front and an abdomen behind. They have eight legs, all attached to the cephalothorax. The legs are fairly long in this family, often twice as long as the body.

On the front of the cephalothorax they have two small "mini-legs" called pedipalps. These are used to grab prey, and they are used in mating. Pedipalps are much bigger in male spiders than in females. In this family all species have eight eyes in two rows of four. Their eyes are small and all the same size, though back row eyes are sometimes oval-shaped and longer than the front row. These spiders have strong mouthparts and their fangs are sometimes a bit longer than other spiders of the same size. All sac spiders have venom glands.

Sac spiders are often rather pale: a common house species is yellowish white, some are even lighter and others are light brown. No matter how pale they are, their mouth parts and the area near their eyes is much darker, usually dark brown.

  • Range length
    5.0 to 12.0 mm
    0.20 to 0.47 in

Where do they live?

This family of spiders is found all around the world, and about 540 species are known. Only about 30 species are found in Michigan.

What kind of habitat do they need?

These spiders climb around on vegetation looking for prey. They can be found in most habitats that have lots of plants. A few species in this family are often found in houses and other buildings.

How do they grow?

Spiders hatch from eggs. The hatchlings look more or less like grown-up spiders, though sometimes their colors change as they age. To grow they have to shed their exoskeleton, which they do many times during their lives.

How long do they live?

Most spiders in this family live for about a year. Females might live longer. Males often die soon after mating.

How do they behave?

Sac spiders are mainly active at night, and they roam to new places every night. They'll only stay in a place as long as they find food there. These spiders are not social. They only come together to mate.

How do they communicate with each other?

Since they are active in the dark, these spiders mostly rely on smell, touch, and taste for communication. They can see, but not very well.

What do they eat?

Sac spiders are aggressive hunters. They search vegetation at night, grabbing, biting, and eating the insects and other invertebrates they find there.

What eats them and how do they avoid being eaten?

Sac spiders spin a little silken room to hide in during the day. Sometimes they fold a leaf over and spin in there, sometimes they hide under a stick or a stone. They are only active at night, so they are hard to see. They will bite to defend themselves if they can.

Do they cause problems?

Though not very dangerous, some species in this family can give a painful bite.

  • Ways that these animals might be a problem for humans
  • injures humans
    • bites or stings

How do they interact with us?

Sac spiders are important enemies of many insect pests.

  • Ways that people benefit from these animals:
  • controls pest population

Are they endangered?

No sac spider species are known to be endangered or in need of protection.

  • IUCN Red List [Link]
    Not Evaluated

Some more information...

Sac spiders get their name from the little silk sacs they make to hide in during the day. They also use the sacs to protect their eggs.


George Hammond (author), Animal Diversity Web.



living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map


living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map


living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.


a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.


an animal that mainly eats meat


mid-altitude coastal areas with mild, rainy winters and long, dry summers. Dominant plant types are dense, evergreen shrubs.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


animals that have little or no ability to regulate their body temperature, body temperatures fluctuate with the temperature of their environment, often referred to as 'cold-blooded'.


An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


generally wanders from place to place, usually within a well-defined range.


found in the oriental region of the world. In other words, India and southeast Asia.

World Map


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Climbing plants are also abundant. There is plenty of moisture and rain, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


living in residential areas on the outskirts of large cities or towns.


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


this biome is characterized by large expanses of coniferous forest, there is an extended cold season and heavy snowfall.


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


living in cities and large towns, landscapes dominated by human structures and activity.

University of Michigan Museum of ZoologyNational Science Foundation

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Hammond, G. . "Clubionidae" (On-line), Animal Diversity Web. Accessed April 19, 2014 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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