10 Interesting Black-Footed Yellow Sac Spider Facts

The name of this particular species of scary spiders gives away a lot about what these creatures look like. The same can’t be said about their scientific name which is “Cheiracanthium inclusum.”

In this article, you’ll discover some of the most interesting facts about the black-footed yellow sac spider, a type of spider that might dell inside your house but that you don’t want to meet any time soon.

1. The history of this spider has been rather confusing

Cheiracanthium inclusum or the Black-Footed Yellow Sac Spider was long believed to be a member of the true sac spider family. This family is known as “Clubionidae.” These spiders built silken homes referred to as sacs.

They were subsequently placed in the Miturgidae family which consists of about 170 species of spiders in 29 different genera.

Today, they are a member of the Cheiracanthiidae family which consists of 363 species divided into 14 different genera. They belong to the genera Cheiracanthium which is referred to as the “Yellow sac spiders.”

2. Its nickname distinguishes it from its European counterpart

The genera Cheiracanthium consists of 212 different spider species and one of them bears a remarkable resemblance to this species.

It’s called the Cheiracanthium punctorium and can be described as the European nephew of the Cheiracanthium inclusum. This spider, however, is also native to Central Asia.

The nickname of the spider described in this article is the “American yellow sac spider.” This distinguishes it from its European and Asian counterpart which looks very similar.

Cheiracanthium punctorium
Cheiracanthium punctorium / Fritz Geller-Grimm / Wiki Commons

3. How big is the Black-Footed Yellow Sac Spider?

These are relatively small spiders and although their leg span can reach a length of up to 2.5 centimeters (1 inch), their bodies are pretty small indeed.

Male spiders have an average body length of 5 and 9 millimeters (0.19 and 0.35 inches). The female black-footed yellow sac spiders have an average body length of between 4 and 8 millimeters (0.15 and 0.31 inches).

4. Where do these spiders live?

These spiders are indigenous to the Americas, including North, Central, and South America, as well as the West Indies. They have, however, spread to other parts of the world, including Africa and Réunion.

They can mostly be found roaming around in the foliage of forests or gardens. During the winter months, they can also be found inside people’s homes or other structures to protect them from the cold.

Interestingly enough, the Cheiracanthium punctorium or the European counterpart of this spider can also be found in the Americas as it was introduced here.

5. Its name reflects its appearance but they have more distinctive features

The small size of these spiders doesn’t mean that they are hard to recognize. After all, the name of the black-footed yellow sac spider gives away much of what they look like, including their yellow-beige shade of colors.

The other distinctive characteristics are the fact that their front pair of legs are distinctively longer than the three other pairs.

They have distinctive dark markings on the edge of their jaws, legs, and their abdomen often features an orange-brown stripe that starts right from the top.

Cheiracanthium inclusum
The American yellow sac spider / Austin Campbell / Wiki Commons

6. You won’t find these spiders roaming around during the daytime

These spiders can be found hiding during the daytime and roaming around at night. This includes just about all activities such as eating and mating.

This makes them true nocturnal creatures that you won’t come across any time soon.

One of the most remarkable facts about the black-footed yellow sac spider is that they retreat to a new nest every single day. They build these silken nests in less than 10 minutes and they can take on different shapes, including with one opening or two openings.

Another remarkable feature of these spiders is that they can use silken threads to move from one shrub or tree to another. Just think about Spiderman and you’ll get an idea of how they move around.

7. They don’t make webs to trap prey but rely on a remarkable feature

Many spiders in the world actively build webs and just sit around waiting until an unfortunate creature passes by. When it gets trapped inside the sticky web, the spider starts its deadly assault.

This is not how Black-Footed Yellow Sac Spiders catch their prey because these are predators that actively roam around to find prey. Their usual dinner (they exclusively eat at night) consists of various insects and other spiders that they can catch.

These spiders are equipped with 4 parallel rows of 2 eyes but the eyesight is rather bad. This is not surprising because they are nocturnal.

instead, they rely on their palps to detect sensory movements of creatures roaming around and don’t hesitate to attack in case it gets too close.

8. Male Black-Footed Yellow Sac Spiders mature faster than females

The male spiders aren’t just bigger than the females but they also mature faster. Males are sexually mature at around 119 days and females at approximately 134 days.

This is just an average number because this can range widely from anywhere between 65 to 273 days. The most significant impact on this number is the living conditions of the spiders such as temperature and humidity levels.

9. Females can produce a large number of eggs

The female spiders only mate once and produce several sets of egg masses (1 to 5). This happens just 2 weeks after mating and each egg mass consists of anywhere between 17 and 85 eggs.

The eggs are usually laid in either June or July and as you surely expected, these are rapped in small silk tubes to protect them. The female spiders constantly guard these tubes as well before the spiderlings emerge.

The mother stays with the juvenile spiders for approximately 17 days, the time it takes for their first molt to be completed. After this, she repeats the process and produced another silk tube for a new batch of spiderlings.

10. Bites of this spider are painful but rather harmless

Are Black-Footed Yellow Sac Spiders dangerous and should you be worried after a bite?

While bites of these spiders are certainly not a pleasant experience, they usually only result in a local swell. This means that the venom isn’t powerful enough to cause serious complications.

Luckily, these spiders don’t bite often and only roam around at night. During the day, they are tucked away inside their silken abode, which is pretty good news.

Spider inside silk sac retreat
A spider inside its silk sac retreat / JMK / Wiki Commons