Samantha Poteet
ENGWR 480
Professor Kiefer
31 October 2013

Little is known about Jakob von Uexküll, the author of A Foray into the Worlds of Animals and Humans: With a Theory of Meaning, other than his credentials and contributions. Uexküll studied zoology at the University of Tartu, known as Dorpat at the time, in Estonia from 1884 to 1889 (SUNY Press; Jakob von Uexküll Centre). Later Uexküll worked at the Institute of Physiology of the University of Heidelberg and at the Zoological Center in Naples, focusing on the behavior and interaction of living beings (SUNY Press; Jakob von Uexküll Centre). His written works were dedicated to the question of how living beings subjectively perceive their environment and how their perception determines their behavior, which is a dominant theme throughout A Foray in the Worlds (Jakob von Uexküll Centre). Uexküll argues that the spider builds its web before it has ever met a physical fly, therefore it is a representation of the spider’s primal image of the fly (159). Uexküll’s claim depends on three assumptions: (1) the fly is the prey of the spider, (2) the spider has a primal image of the fly, and (3) the web is the end product of the spider’s primal image. Though Uexküll’s claim may well have some merit, he presents an incomplete argument as his assumptions are insufficient and based solely on the evidence he offers, his argument cannot be accepted as valid. Uexküll’s first assumption is correct but also insufficient as it does not seem to consider the variation of prey, let alone prey behavior during capture. Handling time, diet, feeding frequency, abundance of prey, prey size, and the nutritional value of prey have been cited as factors that influence the design of webs (Mayntz, Toft & Vollrath; Nakata; "Prey protein"; "Prey type"). It has been stated that spiders rely on the vibrations of the web’s radial threads for cues of prey presence. Moths, bees, wasps, and grasshoppers have been listed as the spider’s prey (“Why cross the web”; Souza, Gonzaga & Vasconcellos-Neto). Wasps, bees, and flies provoke strong vibrations on the radial threads of the web, as they flap their wings at a high frequency in attempt to escape (Souza, Gonzaga & Vasconcellos-Neto). Moths only make movements in small pauses, while grasshoppers are reduced to kicks and body shakes (Souza, Gonzaga & Vasconcellos-Neto). It is easily determined, then, that the spider is drawn towards wasps, bees and flies because of the strong vibrations as a byproduct of their movements. Surely it is possible for other prey to escape if the movement does not emit noticeable vibrations on the radial threads. Given consideration that the spider has prey other than the fly itself, it remains to be empirically established whether the spider has a primal image of the moth, bee, wasp, or grasshopper. Uexkull’s second assumption cannot be accepted as valid as he fails to offer supporting, credible evidence. There is a notable lack of scholarly articles verifying this assumption, as none are related to the topic of the spider’s primal image. As Uexküll did not provide an in-depth explanation in regard to how he reached this assumption, options in academic research remain limited. An extensive search of full-text, peer-reviewed journal articles in English between 2000 and 2013 was conducted using “spider primal image,” “spider image fly,” and “spider image insect” as key search terms. The databases searched were Academic Search Complete, CQ Researcher, Google Scholar, JSTOR, Environment Complete, and ScienceDirect. One possible reason why it has been difficult to find credible evidence supporting Uexkull’s second assumption is the fact that his written works were translated from German to English, and therefore the key term “primal” may have been an incorrect translation. Available research, however, has referred to the vibrations via the radial threads of the web as a key source of information relative to the spider’s environment such as the presence of predators, prey, and wind speed (“Multiple prey cues” 956). Such information suggests that even if empirical evidence verified the spider’s capability of having a primal image to begin with, such a primal image may not be necessary in the response to its prey. Uexküll’s third assumption cannot be accepted as it does not consider any other purposes the web may serve other than the spider’s claimed primal image. It has been well documented that one of the primary purposes of the web is to attract prey, reflecting ultraviolet light to exploit the insects’ color vision ("Why cross the web" 221; Bruce, Herberstein & Elgar). It is a possibility that the web may also emit blue light as well to attract prey, but it remains to be explored and determined ("Why cross the web”). The web also serves several other functions such as regulation of water intake, thermoregulation and delivering environmental cues (“Multiple prey cues” 955; Nataka). Any changes to the web’s design must take in consideration of costs and benefits such as the risk of exposure to predators, the cost of energy, web tension adjustment, and the stabilization of the web (“Multiple prey cues”; Nataka). Spiders rely on airborne cues to pick up the presence of their predators and subsequently devote less time to web-building as a response, simply constructing fewer radial threads and larger silk decorations, which strongly indicates that their webs serve an anti-predator function at the cost of effective prey capture (Bruce, Herberstein & Elgar; Nakata). It is clear that there is a trade-off between safety and the need for prey. Not only does the effectiveness of the web as an anti-predator function depend on its design and size, it also depends on light intensity and background contrast (Bruce, Herberstein & Elgar). It is commonly known that some animals depend on the ability to blend in with its surroundings as much as possible to conceal themselves from their predators and, as the web is also the spider’s inhabitation, the spider is no exception. As it is clear that the spider reacts differently to variations of its environment and prey, Uexküll’s third assumption of its primal image as a factor in the design of the web alone cannot be accepted as sufficient. As much as A Foray into the Worlds of Animals and Humans was brilliantly written, Uexkull’s argument that the spider’s design of its web is based on its primal image of the fly, prior to having met the fly, has some value but overall remains incomplete. Uexkull’s fundamental assumptions cannot be given full credit partially because of the lack of sound empirical evidence and the lack in consideration for other possible explanations. Some questions remain. Is it really possible for the spider to have a primal image of the fly, or for that matter, the prey? What about its predators? Does this apply to other animals or even human beings? Further empirical studies are required to answer those questions.