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Photo of Stim Wilcox Stim Wilcox as seen on Spiders!: Song and Dance

Click on Stim's photo to read a brief bio.

q Is it generally believed that this complex behavior of Portia spiders is completely programmed in their DNA? Charles

A Portia's ability to do all its complex types of behavior, including the ability to solve problems and think on a limited basis, is genetically based, of course. Otherwise they wouldn't be able to do it. Since some of what they do is learn, flexibly, in some circumstances, it's clear that learning is genetically-based too. Most biologists would agree with that. Another way to put it is that they have the instinct to learn. It's rather amazing to see tiny Portia only a few days old doing the complex things adults do. So they have it all built in.

q Do Portia spiders use any other techniques, or parts of their body besides their legs and mouth pieces to pluck the fibers of the web (besides what we saw on SAF)? Students at WAS

A Portia uses its palps (in front of the mouth) -- and not the mouth parts, per se -- for plucking, drumming, etc., as well as its legs; but it also will shake the whole body in various ways. The complexity of Portia's signals comes not only using various parts of the body, but especially in how different parts are used in combinations. We've seen over 100 ways/combinations in which Portia can make signals.

q How can you tell the difference between a male spider vs. a female spider? Adam

A In spiders, all ADULT males have the tips of their palps expanded and/or elaborated, into organs which transfer sperm to the females. The palps of females don't have those expansions. Also, in many spiders the males are different in size, differently colored, differently shaped, etc. The palp expansions are the only sure way to tell in a species with which you're not familiar, if the sexes look mostly the same.

q Why don't spiders get stuck or trapped in their own web? Katy

A Spiders have evolved surface chemistry that enables them not to get stuck in their own webs. But most spiders do tend to get stuck in the webs of other species, especially if they're very different groups of spiders. One of the neat things about Portia is that Portia can move on the web of essentially any spider without getting stuck.

q When Portia jumps on her prey does she kill it with venom? If not what method does she use? Jen

A Yes, Portia kills prey with venom, injected through its fangs. Portia's venom is a very broad-spectrum venom that kills essentially any spider or insect. Portia is also very resistant to being killed by the venom of other spiders. Both are obviously evolved features of Portia's biology.

q Do Portia spiders ever get caught in webs? Greg

A Portia can walk on any web we have ever put it upon. This is a very unusual ability, since most other spider groups tend to stick to webs made by different groups of spiders. Thus the surface chemistry of Portia is pretty special.

q Is the silk we wear and use the same as spider silk? (asked by many viewers)

A The silk we wear is made from the coccoons of a variety ofdomesticated moth species. The silk is spun by the caterpillars in circular fashion, so that the silk is literally unrolled off the coccoon, then woven into fabric. The silk is basically similar to the silk of spiders, however. To learn more about the silk fabric we wear, look up silk or silkworm in an encyclopedia.

q Why are most spider webs formed in a circular shape instead of like a square or oval shape? Students at WAS

A Actually, spiders make webs that are shaped anywhere from circular (orb) webs, to oval, to dome-shaped, to more or less flat sheets, to amorphous, multidirectional "space" webs, to little nets that are "cast" by the spider, to webs with towers or special things like that in them, to simple single strands. There are many sorts of webs/web shapes. A good source of web types and their evolution is a book written by William G. Eberhard.

q I am wondering if you can buy Portia spiders, and if so where? (asked by several viewers)

A There are no suppliers from whom you could buy Portia. Portia is an amazingly hard spider to find in the field if you don't have direct help from an experienced field person, though once you know they aren't very hard to locate. But there aren't very many Portia in any one area in the field, either.

The few researchers working on Portia in the laboratory treasure them highly, as they are difficult to raise and keep, for one main reason: they need a high proportion of other spiders as food. It's very time-intensive work to raise spiders as prey for Portia, as well as to hunt for prey spiders in the field. And in the winter, there aren't any spiders available in the field if you're in northern areas. So the researchers don't have Portia to sell. If we could buy Portia, we'd undoubtedly do that ourselves!

q I thought the spiders program was very unique. I found it very interesting to see how smart a spider really is and to see the different prey-hunting techniques that Portia used. I wondered if there are any other spiders that use Portia's techniques? Albert

A There are a number of other spider species which use Portia's techniques. Almost all the techniques Portia uses are used by at least one other species of spider. These include other jumping spiders besides Portia, as well as spiders in groups that are quite unrelated to Portia. The thing about Portia is that it does all the techniques any of the other species do, and it's fair to say it does the techniques as well as or better than the others.

In the United States, the common long-legged spiders found in most people's basements, Pholcus phalangiodes, is an aggressive mimic like Portia. It will leave its web and go hunting other spiders in their webs, and lure them closely with web-borne signals like Portia does. Also in our country there are other jumping spiders that will use the detour behavior Portia does - see a prey spider, then take a roundabout route to get to it. This takes planning ahead. I suspect most jumping spider species will do this.

q Why do you think the Portia fimbriata developed its cunning techniques? (asked by several viewers)

A We don't really know why Portia developed such cunning techniques. Our best guess is that Portia's excellent vision is involved, in that seeing prey at a distance means Portia can develop, through evolution, the ability to "think" about strategy and tactics before stalking the prey. This would put a premium on problem-solving ability and the ability to plan ahead, which Portia does very well.

q What is the native habitat for the Portia? How long does it live? How many times a day does it eat? McCormick Middle School

A Portia species live naturally from the northeastern part of Australia, in the rainforest, clear through the Malaysian etc island system to Sri Lanka. Other species are found in various parts of Africa. There are no Portia found in the Americas or Europe.

Portia will live about a year in the wild or in the laboratory, starting from the egg.

Portia can eat a spider of its own size about once every 2-3 days. If you give it lots of prey spiders, it will continue to eat them until it looks like it has a balloon for an abdomen. But then it won't be hungry for maybe up to a week. By and large, Portia and other jumping spiders eat much more food than many other spiders, probably because their hunting techniques (locating prey visually, then actively stalking them) use more energy than spiders that primarily sit on their webs.


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