I was amazed to see a familiar spider in Colombia. i worked on this species for 2 years for my Masters in Israel, and now it seems that the spider is an invasive species found all over Colombia. Later at the III Latinoamerican Congress of Arachnology, I found out that Cyrtophora is also found in Cuba, Brazil and Florida. Therefore it must be here in Mexico. Somewhere. Bad news for Mecynogea
I forgot to mention that last year I got a paper out on an orb-web spider that sits upside down in the web. Freaky stuff.
Reverse positional orientation in a neotropical orb-web spider, Verrucosa arenata
Dinesh Rao, Oscar Ceballos Fernandez, Ernesto Castañeda-Barbosa and Francisco Díaz-Fleischer
Abstract
Most orb-web spiders face downwards in the web. A downward orientation has been proposed to be the optimal strategy because spiders run faster downwards and thus can catch prey quicker. Consequently, orb-web spiders also extend their web in the lower part, leading to top-down web asymmetry. Since the majority of orb-web spiders face downwards, it has been difficult to test the effect of orientation on prey capture and web asymmetry. In this study, we explored the influence of reverse orientation on foraging efficiency and web asymmetry in Verrucosa arenata, a neotropical orb-web spider that faces upwards in the web. We show that reverse orientation does not imply reverse web asymmetry in this species. V. arenata spiders captured more prey in the lower part of the web but more prey per area on the upper part. The average running speeds of spiders did not differ between upward and downward running, but heavier spiders took longer to capture prey while running upwards. We discuss these findings in the context of foraging efficiency and web asymmetry.
The blog lay dormant through most of 2011, not only because of a sudden but expected reduction in time available, but also inclination. I did continue my offline blog, my moleskine for travel related entries. I’m hoping that this year will mark a return to blogging.
And therefore, here’s a list of books I picked up North of the Border last month
1. Endless things, by John Crowley. I already had a copy of this book, the last in the Aegypt cycle, but the edition I had did not match. It stuck out like a sore thumb, and it had always bothered me. So this time, I found a copy of the book in the Smith’s Family Bookstore, in Eugene, Oregon and bought it without blinking. This is a new attitude for me: and from on I will replace crappy editions of books I already own and love with nice ones. I’m already regretting not buying a superior copy of Wind, Sand and Stars by Saint-Exupery.
2. Andrea Barrett’s The middle kingdom. I liked Barrett’s previous books, especially Ship Fever, she has that nicely managed mix between science and literature. I bought this book solely on the strengths of the previous ones I’ve read, even though the them of this novel did not particularly interest me.
3. Kleinzeit, by Russel Hoban. Russel Hoban just passed away recently, yet another in the line of favourite authors dying. His The Medusa Frequency has always been a very important part of my collection, and I’ve carried it to various continents. This book was written prior to TMF, but it has a very similar feel to it. I think the three books, TMF, Kleinzeit and The Lion of Boaz-Jachin and Jachin-Boaz make a sort of weird trilogy.
4. Difficult Loves, by Italo Calvino. Nothing much to say here, except this is part of my effort to slowly have every Calvino book in my library.
Conditions Favoring Group Living in Web-Building Spiders in an Extreme Desert Environment
Dinesh Rao and Yael Lubin
Albert Katz International School for Desert Studies, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer 84990, Israel
Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer 84990, Israel
Abstract:
Colonial spiders construct individual capture webs within a matrix of shared supporting frame threads. Cyrtophora citricola is a colonial orb-weaving spider with a complex three-dimensional web. Colonies may contain a few to several hundred individuals, but individuals may also occur solitarily. Local conditions such as food supply and substrate availability are likely to influence colony formation. In this study we explored the influence of local conditions and dispersal behavior on colony establishment in a desert population of C. citricola in the hyper-arid Arava Valley in Israel. Colonies in the Arava occur primarily on scattered Acacia trees and less commonly on shrubs. The spatial distribution of colonies was clustered and was not influenced by the condition of the Acacia trees (leaf flush, flowering, or fruiting). In a controlled experiment, we showed that dispersing spiders remained longer and built webs faster in trees that contained conspecific webs than in trees without webs. We propose that spiders benefit from establishing webs in the proximity of other spiders, while dispersal to another tree may not result in arrival at an improved habitat. These two factors may promote colony living even in prey-poor environments such as the extreme desert.
