Spiders vs. Spiders
Generally accepted as the world's most intelligent spider, the fringed jumping spider (also known as "Portia") is as patient as it is crafty, all with a brain roughly the size of about a quarter of a baby aspirin. In this article, you will learn about some of the different methods this amazing spider uses as a predator and how it, too, can be prey if the proper precautions are not taken. Spiders eat spiders - they are araneophagic, and this particular genus uses carefully thought out, prey-specific tactics when acting as predators.
A Portia Spider's Tricky Hunting Methods
The Portia spider appears to be aware that different hunting methods are required depending upon the skills of its prey, and makes whatever modifications are necessary to ensure its success. For example, when attacking a spitting spider, the Portia attacks from behind - away from the venomous spit of its prey, which could immobilize a predator in only a few milliseconds. The spitting spider is a predator of jumping spiders, and the portia spider appears to be aware of the potential dangers involved in turning the tables on the enemy.
Less dangerous prey (web-spinning spiders) require a different method, and the Portia spider usually mimics either a potential mate or some other defenseless prey and waits in the center of another spider's web (which was spun in order to catch their own lunch). The portia spider, however - as it sneaks to the middle of the web and causes vibrations of the web to get the resident's attention - has something different in mind and waits patiently for the unsuspecting victim.
Robert Jackson of the University of Canterbury in New Zealand has spent a lifetime trying to understand the mind of a spider and has referred to the Portia spider's method as an "aggressive mimicry" (deceiving its prey by imitating something desirable) - he has said that the spider uses "mimicry, detours and deception."
So, what keeps the Portia spider from getting snagged in the web itself? One popular theory is that it has a waxy (or possibly oil-based) outer coating that prevents it from being snagged.
Trial and Error
The Portia spider has the ability to leap up to 50 times the length of its own body, so it's easy to see how other spiders might be unsuspecting of an attack from so great a distance. As the spider jumps, it leaves behind a kind of "bungee cord" line of silk which acts as a safety device in the case of a missed target. In that event, the spider can always simply climb back up the safety net it established and try again later. After all, this predator uses a trial and error method, and seems to remember what does and doesn't work and employs the best of its methods in future attacks.
Springing Into Action
When a jumping spider springs forward to pounce upon its prey, a powerful muscle in the cephalothorax is actually squeezing fluid from the body of the spider into the legs causing them to extend quickly, which allows the spider to jump using hydraulic pressure.
Portia spiders are enemies of bugs in nature. And although spiders do eat their own species, they also eat lots of other insects. They only live about a year and a half, but they apparently try to make every moment count. When they are producing eggs (or have simply eaten a lot), the abdomen is enlarged in all species of Portia spiders.
These smart arachnids, in their own attempt at survival, have been known to mimic ants because most predators prefer spiders over ants. When employing this protective-mimicry method, the Portia walks on all eight legs in a broad path that is meant to resemble an ant following a pheromone trail. The spider pauses occasionally and raises its forelegs in an attempt to mimic an ant's antennae.
The visual capability of jumping spiders sets them apart from other spiders. The eyes of most spiders lack the structural complexity required for acute vision; but jumping spiders have unique, complex eyes with resolution abilities unparalleled in animals of comparable size.
— Robert R. Johnson and R. Stimson Wilcox (from an article published in American Scientist journal)
Small but Deadly to Other Spiders
Stories of a Portia spider eating other spiders may conjure up visions of huge spiders as big as a man's fist attacking the smaller ones of its kind, but this crafty arachnid, when full grown, is only about half an inch long. Size, however, doesn't slow this predator down, as it is known to attack, kill and devour other spiders two to three times its size.
A jumping Portia spider is able to travel undetected across the ground through foliage - simply resembling another leaf - and sneak up to within jumping distance so that it can ambush and sink its poison-injecting fangs into its prey. Very clever, wouldn't you say?
Different Species and Where They Live
There are over 4,000 species of jumping spiders in the world (only 300 species are found in the United States and Canada). This is the list of the 17 species of the Portia genus of spiders (established in 1878 by German arachnologist, entomologist and anthropologist Ferdinand Karsch) and where they are commonly found:
- Portia africana – West, Central Africa
- Portia albimana – India to Vietnam
- Portia assamensis – India to Malaysia
- Portia crassipalpis – Singapore, Borneo
- Portia fimbriata – Nepal, Sri Lanka; and Taiwan to Australia
- Portia heteroidea – China
- Portia hoggi – Vietnam
- Portia jianfeng – China
- Portia labiata – Sri Lanka to the Philippines
- Portia orientalis – Hong Kong
- Portia quei – China, Vietnam
- Portia schultzi – Central/East/Southern Africa; and Madagascar
- Portia songi – China
- Portia strandi – Ethiopia
- Portia taiwanica – Taiwan
- Portia wui – China
- Portia zhaoi – China
- Jackson, Robert R. & Susan E. A. Hallas (1986). Comparative biology of jumping spiders Portia africana, P. albimana, P. fimbriata, P. labiata and P. schultzi, areanophagic, web-building jumping spiders (Araneae: Salticidae) utilisation of webs, predatory versatility, and intraspectic interactions. New Zealand Journal of Zoology. Volume 13: Pages 423–489.
- Lyndsay M. Forster (1977) A qualitative analysis of hunting behaviour in jumping spiders (Araneae: Salticidae), New Zealand Journal of Zoology, 4:1, 51-62
- Harland, Duane P. & Jackson, Robert R. (2000). "Eight-legged cats" and how they see - a review of recent research on jumping spiders (Araneae: Salticidae) . Cimbebasia Scientific Journal. Volume 16: Pages 231–240
- Cross, Fiona R. & Jackson, Robert R., (2016) The execution of planned detours by spider-eating predators. Journal of the Experimental Analysis of Behavior 105:1, pages 194-210.
© 2018 Mike and Dorothy McKenney