Category Archives: Biology

Backyard Friends …a new set of story tales

Last year was another discovery year 🙂 Now from the garden. My backyard was an authentic zoo. We let the wild plants grow and all the little bugs and whatever animals loved it. And I loved that they love it!! There is also a cat coming once and a while. During August, my boyfriend convinced me to buy a biscuit box to blackmail ‘her’ (to me all the nice animals are female …:p), for ‘her’ to come more often. The cat did not like those biscuits that much, especially after they all got moisty during the evening, after raining!

Lesminhas
 
Our Backyard Friends had a party! Actually I think the slugs started it! During the evening opiliones, slugs, snails…they came and loved it! As you can more or less imagine by looking at the pictures.
 
These animals were quite happy eating all the moisty biscuits. (I’ll go into details later, with a video)
 
However, this got me worried. It seemed to me they could not stop eating that stuff..and we could definitely see the slugs growing larger…I honestly thought they could explode!
 
Lesminhas
Lesminhas
 
Backyard Friends ...a new set of story tales
Opilião
 
 
The funny part was that in the end the cat did not come more frequently… Plus….i fell in love with both the opiliones and the slugs..

 

Little ones

 
This is a continuation of the spider tale :)
 
Going back to those days when I kept myself observing and rushing to my bedroom window to check for Madame Diadematus…
Me and my spider…. By observing ‘her’ I end up thinking of how solitary she was and … thinking further, if spiders have a social life.
 
Of course I turn to the web, did my search and in fact they do exist.
1st I landed on wikipedia, on Social spider page.
3rd on a couple of labs doing research on this subject, for example http://www.spiderlab.dk/social-spiders.html. Although a rare trait among spiders, it can happen! There are a few species that indeed share web, nests, capture preys together and there is also evidence of cooperative breeding. Some other species are not permanently social but can have a social period in the juvenile stage, before dispersing. (source: the last link has some references, e.g. Whitehouse & Lubin 2005)
 
I will not go deep into any of this for now. I just want to share some of what I observed. More information can be found by following the weblinks.
 
Going back to my window:
 
Little ones
Little ones’ clusters
After some time, Madame Diadematus disappeared. I was also away for some time, so I lost track of events. … but one day in April the eggs hatched. One day they were born…they must have :). If you look at the pictures you can see groups of tiny spiders clumped together.
 
These little spiders were grouped together for some time, a few days. Every time some strange ‘foreigner’ web vibration occurred they would disperse a little and then when all was calm they would form the groups again. I did not check whether the newly formed groups would keep the same individuals or if they would randomly regroup again…would be nice to check on that! Although I have to say that the spread was not huge…. I thought to myself that this is a kind of social gathering. …or not? Well as aforementioned… they do aggregate right after hatching. I would speculate that …yes, it seems so…but this should be properly tested  😉
 
Little ones
Cluster closer look
They were together I suspect for protection (?). Maybe by grouping themselves they can simulate a larger body and predators (maybe birds? I do not know if they have predators though…) would ‘think twice’ (?).
They were yellow and had a black stain (see pictures). On the other hand would this can attract insects(?) Not sure of what/if they ate!
 
Little ones
 

 

One day the little ones spread and went away. A few days (maybe weeks) later I realize that I have two spiders…one on each corner of my window… probably from those little-one’s groups.
 

 

 
 
  More information and photos:
  1. http://www.nicksspiders.com/nicksspiders/araneusdiadematus.htm
  2. http://animaldiversity.ummz.umich.edu/accounts/Araneus_diadematus/#c1ad1e3a3c216528bde91e44bf5a7f67

Bodysnatchers

(the video is a little speed up)

One of the many phenomena that made me travel in some completely nonlinear route to be doing what I am doing today are spider webs or how spiders construct their webs. I remember reading years ago about a study on the effects of drugs on spiders behavior while building their webs. I was fascinated at the time of course….

In fact the study goes back to late 40’s when Peter Witt, a German-Swiss zoologist working with spiders, became annoyed by the fact that his animal model build its web between 2am and 5am. He asked a friend for help: decided to use drugs to influence animal’s behavior expecting the spider to build its web in a more appropriate hour.

Witt’s intentions did not succeed but he observed that web geometry of the drugged spiders changed. After that he went on trying different drugs, changed some physical quantities like temperature and light exposure conditions and observed the effect on spider web construction (for a review).

The behavior induced by these drugs resulted in different patterns of web geometry. The webs built tended to be specific according to the drug taken. In some cases the web kept its size but were also observed radius irregularities or spiral spacing changes, in other cases the web became irregular and the spiral-like pattern was lost. Other reported effects were changes on thread thickness, web-building frequency and size of catching area.

You can find more on spider web construction here. Here you can also read about some students experiments ….take a look ,) There is one on Arabella and Anita, two spiders launched into space.

References:

Witt, P.N. Drugs alter web-building of spiders: A review and evaluation. Behavioral Science 16 (1) , 98–113 (1971)

A recent one by Fritz Vollrath and Thomas Hesselberg: Hesselberg, T., Vollrath, F. The effects of neurotoxins on web-geometry and web-building behaviour in Araneus diadematus CI Physiology & Behavior 82 (2-3), 519-529 (2004)