* Egg sac, the reproductive structure of spiders

While both the yellow sac spiders and Hobo spider are often claimed to possess necrotic venom, these claims have been challenged.

Cheiracanthium inclusum, alternately known as the black-footed yellow sac spider or the American yellow sac spider ( in order to distinguish it from its European cousin C. punctorium ), was formerly classified as a true sac spider ( of the family Clubionidae ), but now belongs to the long-legged sac spiders ( family Miturgidae ).

Females that produce multiple egg masses build a second egg sac about two weeks after the juvenile spiders disperse.

Some bites are thought to result from a spider mistaking a finger thrust into its web for its normal prey, or in cases where a female is protecting an egg sac, but ordinarily intrusion by any large creature will cause these spiders to flee.

Among the families formerly classified as sac spiders, some of which have common names including the words " sac spider ", include:

* Australian sac spiders, family Clubionidae, Gnaphosidae, Miturgidae, Corinnidae

The long-legged sac spiders ( family Miturgidae ) include nearly 400 species in about 30 genera worldwide.

The anyphaenid sac spiders ( family Anyphaenidae ) are distinguished from the sac spiders and other spiders by having the abdominal spiracle placed one third to one half of the way anterior to the spinnerets toward the epigastric furrow on the underside of the abdomen.

Liocranid sac spiders consist of about 160 species of wandering spiders in 30 or so genera.

The corinnid sac spiders ( family Corinnidae ), like the other clubionoid families, have a very confusing taxonomic history.

* Clubionidae ( sac spiders )

A few spiders of note Hentz classified are the Yellow sac spider and the Southern house spider.

Aysha is a genus of spiders that are often called " sac spiders " because of the dwellings that they create for themselves to take shelter in.

However " sac spider " used on its own should imply a member of the family Clubionidae.

The largest genus currently recognized as belonging to this family is Cheiracanthium, which used to be placed in the family of " true " sac spider, Clubionidae.

Like other members of its family, the whitetip reef shark is viviparous ; once the developing embryos exhaust their supply of yolk, the yolk sac is converted into a placental connection through which the mother delivers nourishment for the remainder of gestation.

An alternative use of the vocal sac, is that employed by the frogs of the Rhinodermatidae family.

The males of the two species of this family will scoop recently hatched tadpoles into their mouth, where they will move into the vocal sac.

Among the families formerly classified as " Clubionidae ", some of which have common names including the words " sac spider ", include:

Hatchling hellbenders are to long, have a yolk sac as a source of energy for the first few months of life, and lack functional limbs.

The presence of a subcutaneous air sac system in at least some pterodactyloids would have further reduced the density of the living animal.

Above both sides of the vocal folds ( the hole and the ligament itself ) are the vestibular folds or false vocal folds which have a small sac between the two folds ( not illustrated ).

Within the Brachycera, several progressively nested groups exist: Eremoneura ( three larval instars ), Cyclorrhapha ( pupation occurs within a puparium ), Schizophora ( flies that escape from their puparium using the ptilinal sac, an evertable frontal pouch ) and Calyptratae ( larger flies with wings that have the calypter, an enlarged basal lobe ).

In the uterus, a majority of monozygotic twins ( 60 – 70 %) share the same placenta but have separate amniotic sac s. In 18 – 30 % of monozygotic twins each fetus has a separate placenta and a separate amniotic sac.

Fraternal twins each have their own placenta and own amniotic sac.

The egg sac is composed of multiple layers of silk and protects its contents from damage ; however, many species of insects have been observed to parasitise the egg sacs.

He asked a woodchuck spirit for help, and she gave him all the hairs off her belly, woven into a magical sac ; which is why woodchucks have bald bellies.

Some species have an enlarged throat sac, which inflates and serves as a resonating chamber when the animals call.

Hatchlings are born with an embryonic egg sac which serves as a source of nutrition for the first 3 to 7 days until they have the strength and mobility to find food.

In the human embryo, the earliest stages of the formation of the amnion have not been observed ; in the youngest embryo which has been studied the amnion was already present as a closed sac, and appears in the inner cell-mass as a cavity.

If the gestation period is shorter, each newborn will at birth still have a yolk sac connected through a slit located on the ventral side of the body wall.

Females never travel far from their burrows, especially if they have an egg sac.

Newborn skinks have been observed consuming their placental sac after birth and will not feed on other food for the first 2 days.

In flowering plant s, the sporophyte comprises the whole multicellular body except the pollen and Ovule | embryo sac In the normal course of events, the zygote and sporophyte will have a full double set of chromosomes again.

Crested Geckos have a small sac for calcium in their mouth.

If an egg laying female does not have enough calcium her sac will be depleted, and she can suffer from calcium deficiency.

They also have a sac filled with churning fire deep within their stomach, allowing them to give literal " warm hugs " to their trainers.

Natterjacks have a very loud and distinctive mating call, amplified by the single vocal sac found under the chin of the male animal.

Unlike the belemnites and other cephalopods, modern nautiluses do not have an ink sac, and there is no evidence to suggest that the extinct forms possessed one either.

Because of the sharpness and thinness of the file the wound was very narrow and, due to pressure from Elisabeth's extremely tight corseting, the hemorrhage of blood into the pericardial sac around the heart was slowed to mere drops.

When seen in the light, the amniotic sac is shiny and very smooth, but tough.

After hatching, the larval are very small and are transparent except for the eyes, yolk sac, and a few colors across the body.

* Dural ectasia, dilation of the dural sac surrounding the spinal cord, usually in the very low back.

In late Fall, an egg sac is made containing up to 50 eggs and put in the very tip of the funnel, protected by the female.

It arises from the posterior crest and adjacent part of the orbital surface of the lacrimal bone, and passing behind the lacrimal sac, divides into two slips, upper and lower, which are inserted into the superior and inferior tarsi medial to the puncta lacrimalia ; occasionally it is very indistinct.