A MEAL FOR EIGHT (LEGS): How spiders catch their food

Our planet is home to around 35,000-50,000 species of spider (the estimates vary), the vast majority of which spin webs made out of silk generated inside the spider’s body. As any arachnid expert will tell you, spiders weave their silky masterpieces primarily as a means of obtaining food. With strands stronger than the equivalent thickness of steel, spider webs are covered with sticky substances that ensnare their prey, trapping flies and even birds and snakes, ready for the web’s resident to deliver its venomous coup de grâce.

When an insect flying about and minding its own business collides with a web, which is often designed to be invisible until it is too late, the impact creates vibrations that alert the spider. Spiders have extra sensitive hairs on their legs, which are attuned to pick up the slightest movement coming from the web’s fabric.

However, arachnologists have not yet figured out how exactly the spider interprets the movement signals when its equivalent of a pizza delivery happens. In 2016, a team of scientists from the American state of Oregon decided to try and solve this puzzle by creating a web of their own.

Using nylon from parachutes, the team built a web that replicated a traditional ‘spoke’ layout, popularly associated with spiders. The strands of yarn were arranged radially and were held taut by a specially constructed machine with an aluminium frame, alongside an attachment resembling a spider placed centrally, as can be seen with garden spiders and orb weavers.

 

 

The vibrations caused by insects were reproduced with the help of a subwoofer-type speaker, and the spiral of the web was emulated with elastic cords. Ross Hatton, a member of the research team at Oregon State University, told GrandesMedios.com, the source of this story, of how realistic they made the web experiment, explaining that they used two different types of nylon rope, just as spiders use two different types of silk.

The artificial spider in the middle was calibrated to pick up vibrations from the speaker, even the slightest ones. As Hatton explained: “We started with the hypothesis that if you moved one of the radial lines slightly, the arachnid perceived that one moved more than the others,

“We also speculated, that the spider would go towards the line that undergoes a variation in its movement”

In other words, Hatton and his team expected the spider in real life to gravitate towards the line of silk from which the most movement was travelling from. However the result of the experiment was quite different from the team’s original hypothesis.

Far from being a simple case of only a single strand of the web notifying that it caught dinner, the team discovered that the cobweb gave off a complex pattern of vibrations, with some sections of the web being more sensitive than others. According to Hatton, at different frequencies of sound from the speaker, different web strands and layouts did not vibrate at all. Different parts and strands of the web vibrated only at certain frequencies and remained unresponsive at others.

These different frequencies of vibration are believed to help the spider identify what type of prey had crashed into its web, and perhaps also help it distinguish between live prey and inedible objects such as leaf fragments and debris. The study, which redrew the way people thought about how arachnids predate, was presented at the American Physical Society conference recently.

SOURCES:

Vijay Shah { विजय }, Twitter, Twitter Inc. https://twitter.com/VShah1984

Tecnología GM, Twitter, Twitter Inc. https://twitter.com/TecnologiaGM

“Cómo perciben las arañas a las víctimas que caen en su red” – GrandesMedios.com/Grandes Medios (6 April 2016) https://www.grandesmedios.com/asi-detectan-las-aranas-a-sus-victimas/

IMAGE CREDIT:

“Spider and web” – Dwight Sipler, Flickr (23 September 2009) https://www.flickr.com/photos/62528187@N00/3948508109/in/photolist-71V8U2-9ReV6c-aqKQGv-dpdK7M-5roAqX-5roEwn-5roBTv-DV9Eq-mYCVp-6Hu2Eb-5tj1DG-9oBvU-jG4wh-8JZa3e-a9A2a9-8WDwtQ-afhCqA-8yN4WL-5vSbKd-e2eBjU-aj8tGX-6QTWyn-4VgnTS-4Vc9mt-9aCUoX-4WYuxd-6bSLvd-51ycz-4rhGUq-31bfxS-316GzT-316xNt-316yCg-31b8K7-31b9dh-31b4TG-316z6p-316wva-31bbq9-31bdXs-31b3iw-31b64m-316EZD-31b7tU-316xwZ-31b8nG-31bdvo-31bcvw-316y1V-31baXE-316w2a

AUROVILLE: A unique city

Auroville, a young city lying around 10 kilometres from the former French colony of Puducherry (Pondicherry), now an Indian union territory, is an important hub of Hindu spirituality, which draws in thousands of people from all over the world. Set deep in the forests straddling the border of Puducherry and Tamil Nadu, Auroville’s buildings are laid out in a unique formation reminiscent of the stars of a galaxy. Designed by architect Roger Anger, Auroville takes its name from Sri Aurobindo, a great philosopher and was established in 1968 by The Mother, also known by her birth name Mirra Alfassa, who was a close disciple of Sri Aurobindo and who hailed from France. Auroville came about as a haven from the religious and political strife of the time, and its whole mentality is geared towards serving God and realising the inner self.

 

 

One of the main ideas that governs the city is the improvement of personal relations among people, at a time when there was much strife and rivalry, and nowadays it encourages the perfection of people collaborating together as one humanity, and the devotees of The Mother and Sri Aurobindo courageously work together to improve relations between different groups of humanity. Auroville even received recognition in this dynamism from once Indian prime minister Indira Gandhi, who spoke of the commune’s work in promoting harmony between different cultures and furthering understanding of how coexistence among human beings can help promote spiritual growth.

According to the Census of India 2014, only around 2,300 people live in Auroville, tiny by Indian standards. Around two-thirds originate from India, France and Germany. They are all governed by the civic cardinal rule, unique to Auroville, which states that no political, religious or spiritual organisation should use Auroville as a platform to proselytise for their faith or recruit followers. As a result, there are no political parties or political operations in Auroville, and there is also no concept of private property or money, with the land and homes held under a communal basis, via the auspices of the Auroville Foundation. Auroville also engages with intra-community activities with neighbouring villages and social outreach work.

Unlike the mayor’s office and local councils found in mainstream cities around the world, Auroville is administered by a committee elected by the locals, and residents can support or veto any measures put forward by the committee without having to deal with council red tape. In return, residents are expected to engage in daily programmes of work, for at least five hours a day, seven days a week, either on their own or collectively. When not working, many of Auroville’s inhabitants like to congregate at the Matrimandir to meditate and pray to and honour God, Sri Aurobindo and the Mother of Pondicherry.

 

SOURCES:
Vijay Shah { विजय }, Twitter, Twitter Inc. https://twitter.com/VShah1984
Tecnología GM‏, Twitter, Twitter Inc. https://twitter.com/TecnologiaGM
“Esta es la ciudad más extraña del mundo: Auroville” – GrandesMedios.com – Cultura/Grandes Medios (21 February 2016) https://www.grandesmedios.com/esta-es-la-ciudad-mas-extrana-del-mundo-auroville/
IMAGE CREDIT:
“File:Auroville puducherry.jpg” – sillybugger/Ian.A, Flickr via Wikimedia Commons (1 May 2008) https://commons.wikimedia.org/wiki/File:Auroville_puducherry.jpg  This file is licensed under the Creative Commons Attribution 2.0 Generic license.