Spider of the Week: the Twin-flagged Jumping Spider (Anasaitis canosa)

This week’s spider is inspired by a beauty that I found in my shower (!) a couple weeks back. Not entirely sure why she was trying to set up camp in there, unless perhaps she was thirsty. Anyway, here are a few glamour shots, plus a couple cool facts about this species. Enjoy the holiday weekend!

Anasaitis canosa from Austin, TX. This species gets its common name from the two large silvery-white spots on the top of its pedipalps.

Anasaitis is a small, currently paraphyletic genus (part of a clade with Corythalia. See: Zhang & Maddison 2013) . Most species are found in the Caribbean, but A. canosa occurs throughout the Southeastern United States.

These spiders are tiny! (Hand and knee of a ~5’8″ woman (myself) for scale).

This species often feeds on ants, as individuals live in leaf litter of forest floors. One observational study of A. canosa‘s hunting behavior found that this species will follow its prey along complex routes, and are perhaps even capable of internalizing and triangulating prey location. See the following paper for more info. It’s a very fun read! Hill 2006 Predatory pursuit of ants.

Like many other spiders, females produce egg sacs that they guard until the eggs hatch. Here’s a picture of my new friend with her newly produced sack. Hopefully I’ll get to see a few little jumper spiderlings sometime soon!

A. canosa female with her egg sac (top right).
A. canosa female with her egg sac (top right).

Last but not least, here’s a great video that makes the “twin flags” and  beautiful iridescence of A. canosa much more apparent.



Spider of the Week: Phidippus texanus (Week 1)

Everyone, meet Linda, my new Phidippus texanus! I have spent way too much time watching/taking pictures of her this week, so I thought that I might as well share with everyone else.

photo 2-1
Linda, bein’ adorable, a few minutes after I first picked her up.

Spiders that belong to the North American genus Phidippus are some of the most well known jumping spiders of the Salticid family, as they are usually rather large and charismatic, and often have bright green chelicerae.

Can see a hint of Linda's green chelicerae in this shot.
Can see a hint of Linda’s green chelicerae in this shot.

Like many animals, Phidippus texanus is sexually dimorphic, in that females are mostly brown with some white stripes on their backside (see below), while males are black with bright red-orange coloring on the dorsal side of their abdomen (see picture here). This extreme coloration is possibly due to years of sexual selection, where male coloring could be a signal of health, good genes, etc… (see more on sexual selection here).

Linda - dorsal view.
Linda – dorsal view.

Anyway, I’m off to go do some DNA extractions for the rest of the afternoon, more info to come on P. texanus in the coming weeks!

Spider of the Week – Black-and-yellow Argiope

For this week, I’m featuring another common, and highly photogenic orbweaver of the Americas: Argiope aurantia. I was out doing field work today, and these spiders were EVERYWHERE! Must be mating time. They are so beautiful, and very large (females can be almost 1.5″ long), so my camera can actually handle taking nice pictures of them. I’m only posting the pictures that I took today, but there are tons of awesome pictures of this species online if you do a little searching. Lots of videos, too.

Adult female Argiope aurantia
Adult female Argiope aurantia

So, what’s interesting about this species, you ask (besides that it is awe-inspiring… )? First, its current scientific name, Argiope aurantia, describes the colors of the spider, as Argiope means “silver-faced” and aurantia is derived from a word meaning “gold” (See wikipedia for a list of its previous scientific names and this website for a longer history of the name “Argiope aurantia”). In the western U.S., this species is commonly referred to as the Golden Orbweaver or the Golden Silk Orbweaver. However, in the southern U.S., this species is commonly referred to as the Black-and-yellow Argiope, and a different species (Nevila clavipes) is commonly referred to as the Golden Orbweaver, causing some confusion as to what the common name of Argiope aurantia should be. Other common names it has are the Yellow Garden Spider, and the Writing Spider, plus varieties of all of its common names pop up here and there. It’s interesting how the same species can have so many different names, presumably because it spans such a large region of the world.

Their webs are nothing short of spectacular. A couple of the webs I saw today had perfect orbs that were almost two feet in diameter, though others were a little more normal, coming in around 6in-1ft. I saw some females sitting directly in the center of their webs, and others were off sitting on leaves or branches about one foot away, waiting for prey to fly into the web (or hiding from me). Curiously, individuals of this species build their webs with a zig-zag (adults) or circular (juveniles) stabilimentum, that is rather conspicuous (at least to humans). There are various hypotheses as to why they might do this, and supposedly these structures inspired E.B. White in writing Charlotte’s Web (See more on the hypotheses here and here).

Adult female Argiope aurantia in web with zig-zag stabilimentum.

Because of their size, capturing large prey isn’t difficult. I saw one capture a very large grasshopper, but I had unfortunately left my camera in the car and couldn’t film it. However, it looked something like this and she did not stop to eat it once she had wrapped it up. Like other orbweavers, she will probably leave it until nighttime, when she takes down her web, and eats it, before building a new one. When I had my camera with me later, I found another web that had a few small insects wrapped up in it (see example below).

Insect (a bee I think) that was wrapped up in an Argiope aurantia web.
Insect (a bee I think) that was wrapped up in an Argiope aurantia web.

This species is NOT a danger to humans, despite how large and brightly-colored individuals are (See this discussion for more info). So, don’t be scared if you see any around in the next few months. Especially since they are so beautiful!

Spider of the Week – The European Garden Spider

One of the things that I love most about my job is the chance to learn something new and exciting everyday, even when I am on vacation. For instance, while I was home in the SF Bay Area last weekend, my dad decided to show me a number of cool spiders that he has found recently while gardening. One of them was this beautiful, and seemingly common orbweaver, Araneus diadematus. I’m sure that I saw this species a thousand times growing up, but being afraid of spiders, never took the time to really appreciate how interesting and beautiful it really is. Here are a couple pictures I took of a male next to my parents’ house, but if you click on a few of the hyperlinks in this post, you can see some professional photos of them. ARKive has some great videos, as well.



Some facts about Araneus diadematus:

  • Commonly known as the “European Garden Spider,” or the “Cross Orbweaver.” The “Cross” name comes from the distinctive pattern on the dorsal side (the “back”) of the abdomen.
  • Occurs throughout North America and Europe.
  • Sexual cannibalism does occur in this species. In this case, females will sometimes eat males either before or after sex, depending on a variety of physical states (e.g. how hungry she is). (See: Roggenbucketal2011)
  • Like many orbweavers, individuals will take down their webs at night, eat the web (along with any insects that are caught in the web), and build a new web in the morning.
  • Spiderlings disperse through a behavior called “ballooning,” in which individuals release a bit of silk that catches in the wind, carrying the spider away from its original home. (More info on ballooning in spiders)

Spider of the Week: The Basilica Orbweaver

A few months ago, my advisor went spider collecting for me, and came back with this really cool species:

Emma5.21.13lemniscata(b) (2)

This beautiful spider, Mecynogea lemniscata, gets its common name, the Basilica Orbweaver, from the domed-shaped, horizontal web that individuals build. While I don’t know everything about this species, here are a few interesting facts that I have learned so far:

  • Females attach egg sacs to each other vertically , and hang them from a thread. Some people even mistake these spider cocoons for butterfly or moth cocoons, as this egg sac structure is not incredibly common in spiders.
  • Females will detach their webs every night, so that they fall onto their egg sacs and provide another layer of protection for their eggs (spider behavior is SO incredible! See Carico, 1984 for more information)
  • Similar to P. oweni, individuals will occasionally aggregate on trees or bushes, in areas with high prey density and numerous web support structures. Some will even share support lines, though they keep their own, individual retreats.  It is likely that they do this to increase prey capture efficiency (See Buskirk, 1986 for more info)
  • The horizontal, dome shape of their webs has caused some controversy as to what family this spider really belongs to, as webs like this are usually characteristic of spiders in the Linyphiidae family. Many orbweavers build the classic, vertical, spiraling webs that most picture when trying to imagine a spider web. However, morphology and behavior tend to place these spiders into the Araneidae family, and most researchers believe, nowadays, that the M. lemniscata web structure is simply a classic example of convergent evolution with the Linyphiidae family web structure.

Carico 1984

Buskirk 1986

Spider of the Week: Philoponella oweni

Uloboridae Philoponella oweni female
Philoponella oweni female (Photo credit: Jillian Cowles)

As I said in my earlier post on misconceptions concerning spider bites, not all spiders contain venom, and Philoponella oweni belongs to one such family of spiders, the Uloboridae. This family of 266 known species (World Spider Catalog) is made up of cribellate (read: spiders with an organ, the cribellum, that occurs between the spinnerets to “comb” through silk as it is produced) orb weavers that are distributed across the globe. Individuals in this family use their finely-combed silk to wrap and strangle prey, as opposed to killing prey with venom, as most spiders do.

Sociality in spiders is incredibly intriguing, given that spiders are often known for being aggressive, solitary creatures. Thus, spiders that deviate from this lonely lifestyle are of interest to researchers like myself that want to understand the evolution of social behavior. Philoponella oweni caught my interest during my early research into sociality in spiders, when I found a few older papers by Deborah Smith that detail this intriguing species’ life history. This orb-weaver is found in the Southwestern United States, and is facultatively-communal, meaning that at times individual females will build nests alone, but at other times, they will connect their nests to those of other females. What causes this difference in behavior? An absence of web attachment sites (e.g. rocks) causes females to attach their webs to the same sites as other females. Though prey-capture and brood care (behaviors found in some spiders with higher levels of sociality) in the communal webs are carried out individually, the females will sit with their egg-sacs in a communal retreat until their young emerge.

So what could this species tell us about social evolution in spiders? What I would propose is that perhaps, when habitats are crowded or scarce, tolerance of others in or near a nest is favorable for this species. What do you think?

For more info read: