Observations on an experiment with spiderlings of
Psalmopoeus cambridgei Pocock 1895
By Carl Portman
Background information:Purpose of experiment:
To study how a community of Psalmopoeus cambridgei spiderlings interact as a group in a relatively confined location. The basic idea is to let nature take its course with limited human intervention. Of course there must be an element of interaction by way of feeding and misting.
Initial set up:
I ‘decorated’ an escape-proof tank 12x10x 8 inches with a substrate of peat and a little vermiculite. I added two moss covered logs collected from an English wood and assembled them in a ‘v’ shape. I also added a small piece of cork bark and two water dishes then heavily sprayed the tank. I deliberately refrained from microwaving the wood and peat. Any bugs contained therein would play a natural part in the macro- environment as indeed would mould or fungi etc. I then introduced the ten Psalmopoeus cambridgei spiderlings. I realise of course that this set up is far removed from natural habitat conditions in Trinidad but I had to use the resources available to me.
The tank looked as follows in figure 1.
There now follows an abridged diary of events.
24/02/97 – Two and a half hours after introduction nine of the spiders have congregated at the top right hand corner of the tank and one is on bark number two. Question; Why did this one not join the others or indeed why did the others not join this one?
The temperature is 24ēc with a humidity level of 80%. Nighttime temperature is to be dropped by 4 degrees. I have personally observed significant night temperature drops in the wild, for example in Ecuador.
02/03/97 – The last few days have seen little change. Nine spiderlings have webbed a marvellous hammock web into the top right corner of the tank and they are all huddled closer than ever together. The solo specimen has webbed itself under leaf ‘A’
12/03/97 – Counted only eight spiders in the top corner today. I introduced micro crickets (black) but only one cricket stayed near the web. The rest have scattered to all corners. Question; Will the spiders starve and is the space too much? Incidentally only one spiderling took a cricket within 5 minutes.
13/03/97 – Action! Only two specimens in the top corner and the rest are perambulating around the enclosure. One has a cricket in the top left-hand corner and three are stationed on log number 1. None are attacking each other.
16/03/97 – Much the same. Dispersed with two specimens found on log number 1, three up in the top right hand corner and the rest (presumably) hiding in crevices. Question; Have they been eaten or died of natural causes? Introduced more micro-crickets.
18/03/97 – Very interesting observation today. One of the spiders has made a large web tube utilising the space available. It has four exits/entrances, which can be shown at figure 2. When the cricket was placed near opening three, the spider raced up the tube and pulled the meal down into the tube. NOTE the cricket was actually two and a half times the spider’s size!
23/03/97 – Several small black crickets were introduced today as well as three large crickets pre-killed. One spiderling has begun to drag a large cricket into its tube web, ignoring the smaller ones. Question; Is it instinct to go for a larger size when it knows there are other competitors in the vicinity? Normally when alone they go for a smaller meal.
12/04/97 – Counted seven specimens today. Two have definitely moulted. I also observed a beautiful tiny snail which the spiders left alone. Recently I have been feeding the spiders on small crickets but today introduced drosphila flies for a change in diet. Not all specimens went for these flies probably because several spiders are about to slough. Temperature still 24ēc and humidity is constant at 80%.
Other spiders beginning to make web structures similar to that observed on 18th April.
18/05/97 – Not much had changed until today when one spider moulted to almost twice its size. An incredible feat indeed and it is now one and a half inches including legs. Question; How do you get a quart out of a pint pot? Answer; Watch the natural wonder of a young Psalmopoeus cambridgei sloughing. Less truly is more!
20/05/97 – I only counted five spiders today. One was on log number three…the first time this has been utilised. I introduced a few more crickets. Question; where have the others gone? They are too big now for nooks and crannies so perhaps they have been cannibalised or simply died. I found no evidence of deceased specimens either on or within the substrate.
27/07/97 – I have not had the opportunity to make so many observations over the last few weeks and today I was able to afford some time to the task. Alas there are only two spiders remaining! The first is one inch long (including legs) and looking quite thin although I had not forgotten to introduce crickets at reasonably regular intervals. The second was two inches long, well fed and ready for a moult. Question; Had it eaten crickets and other specimens? Perhaps there was only one other spider left because the larger spider was ‘full’ of food and could not be bothered attacking it. Both specimens were removed at this point and I considered my experiment finished.Conclusions
Although some readers of this article might find it a little distasteful to have conducted this study I firmly believe it is important to see how theraphosids behave in close proximity. After all, many spiders (and scorpions) are found in colonies in the wild and seem to tolerate each other. It is known that some Poecilotheria species will live together occasionally but I had not read an account of P.cambridgei so decide to have a go myself. I could have tried other methods during this time. For example I could have starved the spiders in order to see if they ate each other. Instead they had a reasonable supply of food. I could have lowered/raised the temperature or humidity but kept both constant. This is why an observation in the wild would be so valuable.I found the fact that the spiders took time to disperse with only one specimen chancing its luck early on to be of great interest. Safety in numbers perhaps? The web structures were fascinating and I never expected four entrances/exits from this species. I was also astonished to observe the smaller tarantula attack the very large prey item (cricket) and drag it into the tube. It must have been incredibly strong to accomplish this.Finally, whilst it was sad to lose specimens (as it is also when they are housed alone) I felt contented that this was a worthwhile experiment. I would love to conduct this type of work in the tarantula’s natural habitat but that would require a very lengthy period of time. In my personal opinion, not enough information of this type is available to enthusiasts and it would be interesting to discuss some sort of project for the future whilst we still have some habitat left. There is so much work to do out there…