Dear Colleagues,
I was wondering if someone who has had plenty of experience experimenting with pitfall traps as a method of collecting arthropods (especially spiders), could share his/her experiences regarding: 1) Does the material that the pitfall trap is made off, affect its ability to capture spiders? To be more precise is glass better than plastic or vice versa? and 2) Does the nature of the fluid used inside the pitfall trap, affect its ability to capture spiders? To be more precise, which of the different fluids used viz, supersaturated saline, alcohol, water, ethylene glycol, formalin, etc are more efficacious? P.S, I managed to locate one article detailing a comparison of the different fluids used in the pitfall traps but, I suppose actual experiences are sometimes more informative as compared to controlled studies. Thank you.
Hello Kumail;
You don't mention the size range of the spiders you are studying. You might search for the name David E Bixler. He studies wolf spiders and thinks that the mouth size of the trap is the major consideration...up to 10 cm in mouth diameter. The spiders seem unable to climb out.
I study ants using pitfall traps of about 3 cm dia. The size choice is based on statistical considerations of sampling effort. Here is a source for the idea.
Borgelt, A., and T. R. New. 2005. Pitfall trapping for ants in mesic Australia: the influence of trap diameter. J. Insect Conservation, 9:219-221.
The fluid choice doesn't matter much if it is non-volatile. In that way olfactory cues are neither attractive nor repulsive.
Good cheers, Jim des Lauriers
If you want to use the specimens for molecular analysis, the kind of the solution is really important. I suggest you use ethanol or propylene glycol. If you just want to capture them for morphological analysis, you can simply use water plus some drops of washing liquid, I'm working on ground beetles, but I capture more spiders than ground beetles in my pitfall traps!
Working on spiders would be very exciting!
In general I find that glass doesn't allow beetles or spiders to climb out, even when the trap is set with a benign interior rather than a fluid (for educational and non-lethal sampling). Plastic I've tried once or twice, and it's much more variable - often the surface is very much easier for things to climb, although I dare say that some lab plastics will be effectively as smooth as glass. In any case, you want an overhang at the top, of course, rather than entirely vertical sides.
Dear Mr. James Des Lauriers,
Thank you for your reply. That is a very interesting observation indeed. The mouth size of the trap can be important. You are using traps to catch ants? Let me share an observation of mine: We once used plastic bottles to setup an arboreal trap for mosquitoes. The trap was baited. We made a glucose solution and added yeast to it and poured the mixture in the trap. The idea was to attract mosquitoes that would come to the CO2 emanating from the trap. Strangely, we caught no mosquitoes but large amounts of ants. Thank you.
Dear Mr. Aref Alikhani,
Thank you for sharing your interesting observations. So that means you have had good success catching spiders by using just water and soap. Point noted. Thank you.
Dear Mr. Joseph Botting,
Thank you for sharing your observations. Does the overhand prevent the catch from leaving? I will try to use both glass and plastic.
Kumail;
In regard to your last sentence to Botting, to keep rain and litter out of the trap I make a square stiff plastic roof with 4 long nails in the corners to make a roof. Push the nails into the soil over the trap leaving about 2 cm. space under the roof and arthropods can freely move under it but the cup is protected.
Cheers, Jim
Yes, I captured a lot of spiders just using water + dish-washing liquid (some drops) in my pitfall traps.
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