Salticids more commonly known as jumping spiders have a highly developed vision in comparison to other spiders. The reason for this is because of the large anterior median (or principal) eyes that these spiders possess. These large eyes allow for an excellent way to understand the three dimensional environment in which they live (Choe 1997). Salticids are known to choose secondary objectives and not primary objectives when hunting prey. Second objective choice differs between salticid species (Tarsitano and Andrew 1999).

In this paper I plan to discuss some jumping spiders of the genus Portia. Portia spp. are unusual because their prey preference happens to be other spiders. Portia have developed some interesting behavior patterns that make them successful in hunting spiders as apposed to insect prey. These ararneophagic spiders are commonly referred to as aggressive mimics. A "cryptic stalking" technique where the spiders morphology is used to alter the individuals appearance to that of web debris (Shear 1986). Portia actually mimic the movements of insect vibration when invading alien webs (Jackson 1992.) Fixations or pauses are more common in Portia spp. than other jumping spiders when scanning as well (Tarsitano and Andrew 1999.)

The differences of Portia to other salticids does not stop at hunting behavior. The female of these spiders readily cannibalizes the male spider during both pre and post-nuptial encounters. If the males is killed before copulation is completed, the males sperm is removed and the male then is eaten. If the female kills the male after copulation the sperm is kept for fertilization and the male is eaten. Not all of the males are killed during sexual encounters but it definitely is the majority of them. Portia are also unusual because they build large webs. Web building is not at all common in salticid spiders. They use these webs to catch insects. P. fimbriata actually constructs two different types of web. Many have hypothesized that Portia show the link between web spiders and cursorial species in an evolutionary sense. Portia or similar spiders like them were the first to leave their webs and to take on cursorial hunting strategies (Shear 1986.)

Jumping spiders (Salticidae) are the largest family of spiders. There are more than 4000 explained species that have been described. Salticids are known for there excellent vision and elaborate courtship behaviors. These two differences truly set them apart from other families of spiders (Choe 1997.)

The large anterior median (or principal) eyes and six smaller lateral or (secondary) eyes are what give the salticids their excellent vision. The function of the smaller posterior lateral eyes has yet to be uncovered. With the four other lateral eyes the spiders are able to detect movement. The principal eyes are for discrimination of objects. The spiders turn so that the desired object falls onto the retinas of the principal eyes. With the spider oriented toward the desired object whether that be prey, mates or conspecifics of the same sex, the spider is able to discriminate between these different objects, exactly how this is done is not well understood (Shear 1986.)

In regard to vision many have done research on how salticids hunt their prey. Because to an outside viewer these hunting behaviors look far too complex for a spider to be implementing them. On closer inspection one observes that the spiders are continually scanning their environment. This behavior is called "spontaneous activity " because the spider is constantly scanning its environment whether there is a stimulus or not (Tarsitano and Andrews 1999). The real question though is; how does the spider know how to get from point A, to point B? Hill in (1979) suggested that the spider chooses a "secondary objective." The principle is that the spider lets say selects a tree branch and then chooses a direction that would bring it closer to this secondary objective. After reaching this "secondary objective" it reorients to the prey item then selects another secondary objective that is closer to the prey or lure. Each completed detour results in smaller and smaller segments until the prey or lure are reached. Tarsitano and Jackson 1993, 1994, 1997).

Salticids respond to conspecifics with courtship or threat displays. Prey, usually motile insects, are actively pursued by some combination of stalking, chasing and leaping. Once the prey has been captured the spider inserts its fangs and holds the prey item until the venom takes effect (Shear 1986).

One can imagine that the family Salticidae must have a large amount of variation within its members. This assumption could not be closer to the truth. One genus of specific interest is Portia. Members of this genus are far from the run of the mill jumping spider. These spiders have interested many researchers because of these striking differences in behavior. The first and for most of these is that Portia create webs, most of the salticids are cursorial. Secondly these spiders are ararneophagic in other words they prefer other spiders as prey. P. fimbriata actively seeks out a prey other salticid spiders and has developed specific behaviors that make it quite successful. Portia belong to the subfamily (Spartaeniae). Four genera of this subfamily Portia included practice something called vibratory aggressive mimicry. Where the spider enters a another spiders web and produces vibrations on the web to the resident spider. Eventually this behavior yields the resident spider as a meal to the web invading spider. The last major difference in Portia has to do with cannibalism by the female after or during mating. The discussion of this paper will go into the details of each of these listed behaviors, as well as other specific behaviors that the members of Portia have developed (Jackson 1992).

In the introduction it was stated that members of Portia make webs. The species of Portia that has been studied most in terms of web building is P. fimbriata. P. fimbriata is a relatively large salticid (adult male body length 5-6 mm and female adult 7-10 mm) colored in a mixture of blacks, whites, pale yellows and oranges. P. fimbriata has been recorded to make two types of webs. Type 1 webs are built by all sex/age classes, are horizontal platforms that are roughly two to three times the length of the spider. Type 2 webs are spun by adult and juvenile females. These webs are quite large, reaching sizes on the order of 4000 cubic centimeters. These webs are unusual looking akin to a cone placed on its point with one or more dried dead leaves dangling at the top flat surface.

The type 1 web is constructed by repeatedly bridging a gap until a platform is constructed by the thread. The building of the Type 2 web takes quite a bit more effort however. The spider first attaches a strand to a carefully selected cup-shaped leaf. With this line it ascends a nearby stem tree trunk or what ever suitable substrate exists. The spider than repeatedly climbs the substrate and puts a line to the ground. After many lines are created the spider than starts to connect them making a three-dimensional. When the structure is suitable, the spider hoists up the leaf to the top of the web. Then the concentration of this web-building goes to the area surrounding the leaf and many sheets of silk are put there. The time to build a type 2 web takes on the order of 2 hours but in laboratory conditions the spiders make adjustment and additions to the webs daily. Cohabitation takes place in these webs the adult male usually with a sub-adult female.

The main reason for these webs does not seem to be catching prey items, because P. fimbriata is ararneophagic. The spider will however eat a caught insect if the opportunity arises. The spiders use these webs mostly for courtship and mating principals. Some of these male and female cohabitations can last many molts. This behavior is also seen in web-building pisaurids where the cohabitation continues long after molting (Shear 1986).

Prey Capture Strategies:

Members of Portia have devised many cleaver way to capture the spider that they actively hunt. The most obvious of these is the cryptic coloration and morphological features that the spiders harbor. These spiders look much like web debris. With many fringes and tuffs of hair on the legs and abdomen and with keen coloration schemes these spiders are truly camouflaged. It does not stop there though, these spiders take a specific rest posture. This "cryptic-rest posture" improves the spiders concealment considerably. This behavior changes the outlines of the spider so that it does not even look like a spider (Shear 1986).

When the spider is in locomotion one may notice very quickly that it does not even move like other spiders. The spiders move slowly rocking back and forth much like that of a mantid. While these choppy motions are going the spider is waving its palps and legs. There is no apparent synchrony between palp and leg waving and the choppy motion both seem to be independent. The full behavior appears to mimic that of a shuttering leaf in the wind. The perfect crypsis for a forest canopy lifestyle (Shear 1986).

Vibratory aggressive mimicry also known as (nest probing) is another one of the many tricks that Portia has up its hairy sleeve. Most of the research on how these spiders hunt has been done using P. fimbriata. This behavior is basically being able to manipulate a resident spider that you are not in the web or to coax the spider to you. P. fimbriata takes on a three part strategy when it is faced with a spider. (1) If the resident spider is small attempt to draw the spider to the edge of the web. (2) If the spider is large keep the spider in the web but avoid predatory attack. (3) When on the web of any size resident spider offer a vibratory smoke-screen to avoid detection. With these three separate strategies in mind P. fimbriata attempts to capture a resident spider (Tarsitano, Jackson and Kirchner 2000).

P. fimbriata has three different methods of silk manipulation. The first of these is a steady strong vibration done by using one or more of the spiders legs on the web. This behavior has been shown to only be used on the outer most parts of the web. The second method is the use of faint silk manipulation. The spider uses one leg or maybe even just one palp when implementing this technique. This type of manipulation is used throughout the web. The last is a strong rocking of the web. The spider creates this rocking by getting its abdomen up off of the web and then quickly crouching. The rocking behavior is only done when in proximity to the resident spider. It is still perplexing to everyone what exactly each behavior is or isn’t telling the resident spider of the web about P. fimbriata. All we know is that it certainly works and most of the time in the favor of P. fimbriata (Tarsitano, Jackson and Kirchner 2000).

Cryptic stalking of other salticids is really P. fimbriata’s claim to fame. The goal of the spider is to sneak up behind the prey spider. Another specific cryptic behavior is used here. The spider wave its palps and gently waves them. At the same time the spider extends its front legs way out in a waving motion and slowly follows its prey in its characteristic choppy gait. If the prey spider turns around P. fimbriata freezes and waits until the spider turns back around. During this freezing the palps are retracted. This retraction of the palps is theorized to conceal the identity of the spider. When the prey spider turns back around P. fimbriata resumes its slow chase eventually sneaking up behind and pouncing down and subduing the prey salticid. P. fimbriata prefers to hunt cursorial salticids over any other type of prey. No other member of Portia does both nest probing and cryptic stalking. This is probably due to the locally abundant prey in P. fimbriata’s home environment (Shear 1986).

P. fimbriata has a more specific behavior toward a specific species of spider as well. A species of Euryattus is sympatric with P. fimbriata. Most salticids make a tubular silk nest, Euryattus is an unusual salticid, because this particular species suspends a rolled up leaf by heavy guy-lines from a tree, rock or other substrate and use the leaf as a nest. The female waits inside the leaf for a male. The male courts the female by going and shaking the leaf. The waiting female then comes out of the leaf and then mates with the male. P. fimbriata takes advantage of this by going down the guy-lines to the leaf nests and shaking them. When the female comes out P. fimbriata captures the Euryattus female and eats her (Jackson 1992).

P. fimbriata has also been observed making undirected leaps. Recent research has shown that this is in response to chemical cues by prey. These leaps are not seen after the spider has located the prey. The current thinking is that this is a speculative hunting device. In other words this leaping is a device for locating prey. When the spider leaps the visual cue is given to the prey item and in turn the prey item then will give the predator visual cues (Clark, Harland and Jackson 2000).

All of these behaviors by P. fimbriata have been seen in the laboratory. The environment in which they are reared has no effect on these behaviors. The spiders are born with these specific behaviors. When other members of Portia are shown or raised with salticid prey they have never performed any of the salticid specific capture techniques that P. fimbriata uses (Jackson 1992).

This small discussion goes to show that P. fimbriata is a true champion at aggressive mimicry techniques. The other members of Portia are all excellent web-invaders. Taking advantage of a spider at home in its web using a repertoire of techniques Portia takes its chances and usually come out the victor (Tarsitano, Jackson and Kirchner 2000).

It should be no surprise to you by now that Portia has a different mating behavior and strategy than most other if not all salticid spiders. When most salticids mate the male mounts the female. This is simply not the case in Portia. The female drops a dragline after the male mounts and the pair mate while suspended in mid-air. This has been observed on occasion in other salticids but mating on the dragline is considered a rarity. In Portia mating is done this way virtually every time (Jackson 1992).

In two species of Portia there is a slight twist on the matter. In P. labiata and P. schultzi the females attempt to kill the males after mating by making twist lunges at the male. In a twist lunge the female rotates suddenly around with fangs open, grabs hold of and kills the male, then eats him (Jackson 1992). The female of these spiders readily cannibalizes the male spider during both pre and post-nuptial encounters. If the males is killed before copulation is completed, the males sperm is removed and the male then is eaten. If the female kills the male after copulation the sperm is kept for fertilization and the male is eaten. Not all of the males are killed during sexual encounters but it definitely is the majority of them (Choe 1997).

The males of these two species appear to be more skittish around females compared to other salticid species. The males of P. labiata and P. schultzi are prone to leap or even run away if the female makes the slightest of motions. This skittish behavior is not seen in P. fimbriata which do not twist lunge. The males of P. fimbriata are receptive to the female and are not prone to run and leap away (Jackson 1992).

P. schultzi and P. labiata females unlike other salticids have specific courtship displays in which they solicit males. The disturbing thing is these look very much like a "cryptic stalking" behavior. Females who mate are not likely to mate again, however they readily show the courtship displays. Sub-adult females mimic adult females and court males. Once the male has mounted the young female, she attempts to twist lunge at him while he tries to copulate (Jackson 1992).

Portia of much interest to many because of the possible evolutionary link that they are between cursorial salticids and web-building spiders. These spiders seem to be at home both in and out of the web and implement a wide array of behaviors that make them successful as a genus. It is thought that ancestors of modern salticids were very much like Portia. First using web-invading skills to hunt other spiders then becoming a fully cursorial species. One major and definite major difference again in salticids is the fact that they are visually oriented. This suggests that web-building spiders were pressured for a more visual existence. Without being visually oriented many of the major salticid behaviors could not occur (Shear 1986). That disagrees with the hypothesis that behavior precedes morphology. Therefore it is increasingly hard to devise a clear pathway without implementing the visual apparatus as a key component in going into a cursorial existence.

Another interesting question is in regard to the behavior complexity of Portia spp. It is noteworthy to say that aggressive mimicry on other spiders is not the safest of behaviors. The spider is at danger of being preyed upon by the resident spider. As described in the previous sections many intricate behaviors must be implemented for the spiders to be able to persist. In fact the Euryattus spider that P. fimbriata is known to specialize in has a defensive behavior against P. fimbriata. When P. fimbriata attempts to entice the female she quickly comes out of the leaf-nest and attempts to knock the spider off of the leaf. When this behavior is implemented P. fimbriata always gives up and searches for another prey item. With all these problems why choose behavioral complexity (Shear 1986).

When looking at Batesian mimics in relative numbers they are only successful when relatively rare. In regard to behavioral complexity it is much the same because they are relatively rare as well. The success of Portia depends on the relative abundance of the spiders. If they saturate an environment spiders may be able to perceive their presence easier. When the spider is found out it has lost. However, with the many techniques that Portia posses losses are few and the resident spiders are usually fooled to their doom. Using the variety of signals and feeding methods, the aggressive mimics can exploit many different types of prey. This in itself reduces the contact that Portia has with other spiders and increases its survival (Jackson 1992).

Choe C., Jae. The Evolution of Mating Systems in Insects and Arachnids. Cambridge University Press pp. 340-351 (1997).

Clark, R., Jackson R. and Wabb J. Draglines of assessment of fighting ability in cannibalistic jumping spiders. Journal of Insect Behavior vol. 12 No. 6 (1999).

Clark, R., Harland D. and Jackson R. Speculative hunting by an araneophagic salticid spider. Behaviour 137, 1601-1612 (2000).

Jackson R. Eight-legged tricksters: spiders that specialize in eating other spiders. BioScience vol. 42 No 8 pg 590-598 (1992).

Jackson, R. and Harland Cues by which Portia fimbriata an araneophagic jumping spider distinguishes jumping spider prey from other prey. The Journal of Experimental Biology 203: 3485-3494 (2000).

Jackson, R. and Clark R.J. Self recognition in a jumping spider: Portia labiata females discriminate between their own draglines and those of conspecifics. Ethology, Ecology and Evolution 6: 371-375 (1994).

Jackson R. and Clark R.J. Dragline-mediated sex recognition in two species of jumping spiders (Araneae Salticidae) Portia labiata and P. fimbriata. Ethology, Ecology and Evolution 7: 73-77 (1995).

Jackson R. and Tarsitano M. Influence of prey movement on the performance of simple detours by jumping spiders. Behaviour 123 (1-2) pp. 106-120 (1993).

Jackson R. and Tarsitano M. Araneophagic jumping spiders discriminate between detour sites that do and do not lead to prey. Animal Behaviour 53, 257-266 (1997).

Jackson R., and Wilox S. Observations in nature of detouring behavior by Portia fimbriata a web-invading aggressive mimic jumping spider from Queensland. Journal of Zoology London 230 135-139 (1993).

Shear W. Spiders, Webs, Behavior and Evolution. Stanford University Press, California pp. 232-268 1986.

Tarsitano, M and Jackson R. Jumping spiders make predatory detours requiring movement away from prey. Behavior, 131, 65-71 (1994).

Tarsitano M. and Andrew R. Scanning and route selection in jumping spider Portia labiata. Animal Behaviour 58: pp. 255-265 (1999).

Tarsitano M., Jackson R. and Kirchner W. Signals and signal choices made by the araneophagic jumping spider Portia fimbriata while hunting orb-weaving spiders Zygiella x-notatainzosis geniculatus. Ethology 106, 595-615 (2000).

Willey, Marriane B. Olfactory cues from conspecifics inhibit the web-invasion behavior of Portia web-invading jumping spiders(Araneae: Salticidae) Canadian Journal of Zoology vol. 71, 1993.