Tammy 9 Jul 6:45 AM

The Challenge
Martin asked What evidence would you or your students accept to support the contention of which strategy; sit and wait or go looking, might be selected for?

I have been thinking about this and the more I consider it the more questions come up. Before evaluating these strategies I think I would need to know a lot more ....Spiders who use webs to collect prey eat what is caught. But do they eat everything that is caught. My initial thought was to start by counting the effectiveness of the webs in catching prey as compared to the number of catches made by the hunters. BUT

1. Are some "catches" not palatable. The book talked about purse spiders netting aside a critter that was not palatable and in another spot talked about wasps with a nasty taste. So gross totals of critters captured in a web may not be valid..

2. How much can a spider eat in one day? There was a reference to spiders surviving without food for a number of days. Is this generally true of genus specific?

3. The web spider has a really good day with lots of catches. Some of them are wrapped and stored. But for how long is a stored prey edible?

4. Do all web spiders store their extra's?
Here is the scenario. Spider A caught 8 critters in its web but only three were edible.
Spider b only caught 4 creatures and 3 were edible.

Do you say they were equally effective. I wondered about the energy spent in housekeeping (getting rid of the useless catches and repairing the web.) With regard to the active hunters, How accurate are they in terms of getting edible prey. Do they spend any energy on non edible prey? My guess would be no so they could be considered the more efficient. And I do realize that the answers may vary among the many types of spiders. A second set of considerations concerns how you would go about making these observations. Spot checking the contents of a web may not give a true indication of results. What if the spider has already eaten and done its housekeeping. What looks like an empty web might be one ready for the next kill. And how do you know what a purse or funnel web spider has inside its web.

Keeping track of the diet of a jumping spider is another problem. If you are lucky to see it inaction that is one thing but how do you know what is happening the rest of the time. Do spiders have particular hunting times -- I know there are nocturnal hunters and daytime hunters but are their certain times of the day (or night ) they are more likely to be hunting.

The book talked about how spiders have split second timing in terms of pouncing. How do you know what it got since there is really no time between its targeting and eating? I am thinking of Diane Fosse spending hours just observing her gorillas. Do arachnologists spend their hours just staring at a piece of territory observing a spider? And how do you observe subterranean spiders... or those that live under the tree bark. Even those that live in leaf litter.... if you move the leaf to see the spider haven't you changed its environment?

I guess controlled experiments could be done in a lab situation but how real a setting can be setup? In terms of field work, is data collected on a rainy or just damp, or cool day significantly different from that collected on a warm or dry day. It seems to me that each condition sets up different results.
There must be spiders that hunt in the rain.... in rainforests at least.
So many things to consider. And I have lots of other ideas along this line.

Bottom line -- I have a deeper appreciation for the work arachnologists (and entimologists) do. It is one thing for me to identify a critter from an enlarged picture. Quite another thing to even see it in the wild!
I would need a web cam in my garden with an option to zoom in and record over a long stretch of time......