12 de mayo de 2020

A unique and interesting find…..

On 1/5/20 I found something that completely blew my mind. I was at a local balancing pond on the Coopers Edge Estate SO874163 when I came across an Alopecosa pulverulenta female with her egg sac. It looked like she was in the process of rotating the sac as it was positioned under her sternum and being held in her chelicerae (photo 1). Her imitation of that other grass dwelling species Pisaura mirabilis, was very impressive indeed. After taking a couple of photographs the spider ran off, although in a rather ungainly fashion due to the way she was holding her egg sac. It was then that I noticed that rather than one sac, the spider was actually carrying two (photo 2). To say I was shocked is an understatement and I stopped her disappearing into the undergrowth by blocking her path with my hand. She then changed direction and started to head towards the shorter patch of grass that I had originally seen her on. This helped me twofold by making it easier for me to photograph, (it’s no easy chore chasing Lycosids through grass, especially with my knees) and also there was less chance of me losing the spider. I took several photos of her in her natural habitat (photo 3 & 4) before collecting her and popping into a container. I then packed up my camera equipment and made the five minute walk back to my home thoroughly excited with my find. Once home I started to look carefully at the egg sacs under a 10x magnification hand lens. From experience I can see that the white sac was produced by A.pulverulenta as it has the shape and structure of a golf ball which is typical for a freshly produced egg sac of that species. Initially, I believed the second sac and obviously the older one, was produced by a Pardosa species but must confess to having reservations about this now. Both sacs have been welded together with silk and the fresh sac is indented by the older sac. I can only surmise as to how she ended up with two egg sacs. One theory is that the A.pulverulenta found the older discarded sac shortly before she was due to produce her own sac and the innate maternal instincts kicked in thus causing her to attach the sac to her spinnerets. Whatever the reason for her having two egg sacs, this seemed a very unique find. For the next several hours I searched through the literature regarding this behaviour or even a similar image of a Lycosid with 2 sacs but this proved fruitless. What my search did throw up was a remarkable image of an ichneumon wasp, Gelis species emerging from a Pardosa species sac that was photographed by Chris Ernst in the Yukon territory, Canada. Why would this seem remarkable to me? Well, after studying the egg sacs and looking at the photos I had taken, I noticed two tiny holes in the older egg sac (photo 5 & 6) which looked remarkably similar to those in Ernst’s photograph (Ernst, C. 2012). From my experience, these holes were not caused by spiderlings emerging and besides, it would be far far too early for emerging lycosid spiderlings if we consider the egg sac was produced this year. . I also did not believe that these were caused by wear and tear as the lycosid egg sac is extremely tough and durable. Was the Pardosa sac discarded due to parasitoids? If so, the two small holes would suggest that the progeny of the parasitoid had emerged and the sac was now empty. An interesting study by Joe Bowden & Chris Buddle showed that in the Yukon territory, Pardosa species egg sacs are relentlessly parasitised by Gelis species (Bowden & Buddle 2012). Whether the older egg sac that the A.pulverulenta is carrying had been paraitised remains to be seen and although I have been very tempted to remove the sacs to investigate I have decided to leave them be until the young spiderlings emerge from the fresh sac. Until that time, the A.pulverulenta has been set up in a cosy enclosure.

Ernst, C. 2012 : The Wolf Spider Parasite - The Bug Geek.

Bowden, J J. & Buddle, C. 2012
Egg sac parasitism of Arctic wolf spiders (Araneae: Lycosidae) from northwestern North America.
The Journal of Arachnology Vol. 40, Issue 3 (Nov 2012), pg(s) 348-350

Publicado el 12 de mayo de 2020 a las 09:28 AM por turnfear2fascination turnfear2fascination | 1 observación | 0 comentarios | Deja un comentario

Spider on a stick!

On 07/05/20 at the pond I found a female Alopecosa pulverulenta that had apparently lost her egg sac and was now running around with a small piece of plant debris as a substitute! Trying to capture a photo of this proved harder than anticipated and nearly all photos seemed to show a spider running over a stick! Eventually I got a shot that I was half happy with.. I then decided to try and capture an image of the spider on my hand and after several attempts was successful and shows the attached plant debris clearly.. Illustrious arachnologists and naturalists have had a fascination with mother Lycosids innate maternal instincts and her willingness to accept foreign objects over her own egg sac and countless experiments have been conducted. George and Elizabeth Peckham found that after removing an egg sac from a Lycosid, she would readily accept it back after 16/17 hours and as long as 24 hours but after 2 days the female would ignore it. English arachnologist, teacher and linguist Theodore Savory noted that the female lycosids urge to attach a substitute to her spinnerets was greatest shortly after laying her eggs. By all accounts this urge would abate over time.. English naturalist and arachnologist W.S Bristowe's experiments involved substituting the female lycosids egg sac with small snail shells and rabbit pellets! . French arachnologist Pierre Bonnet noted that female lycosids would accept rounded objects of variable colour, shape or size. Obviously my Alopecosa pulverulenta who was carrying an item that was quite the opposite to round hadn't read Bonnet's "L'instinct maternel des Araignées". We now come to French naturalist and entomologist Jean Henri Fabre! Sadly, whilst reading through all the previous arachnologists experiments, although they quote each other, not once do they mention the extensive experiments that Fabre conducted and which were done many years before the others.. Fabre's book The Life of the Spider is remarkable and reading through his experiments and observations gives us a real understanding of his passion. This is a guy that Darwin in the "Origin of Species" called “that inimitable observer.”
There is a common theme that runs through this post and that is all the observations and experiments were on captive specimens and not observed in the natural environment. So that is why, I was so doubly excited by finding this specific Alopecosa pulverulenta at the pond and doubt very much that I will see this behaviour again in a natural setting.
Fabre's book can be read online and please visit chapter 3: The Narbonne Lycosa and marvel at his exhaustive observations and experiments!

Publicado el 12 de mayo de 2020 a las 07:54 AM por turnfear2fascination turnfear2fascination | 1 observación | 0 comentarios | Deja un comentario