The Itsy-Marginal Spider, Climbs Up the Temperature Gradient

In my yard in Pennsylvania, there is a sudden explosion of spiders that are bright orange, bright yellow, and black. I have never seen such creatures in my yard before this year.

Why are they suddenly here? There are several possible answers, but among those I thought of was "Global warming: perhaps my yard was out of their range until just recently, but they have been moving north or up in elevation."

And then I wondered just how spiders would know that they could move north? Were they getting weather reports? Little arachno-capitalist real estate agents were pitching them space between my fence railings?

And then I realized the answer lies in marginalism: in whatever range the spiders can occupy, there must be some spiders who are just on the edge of making it: they are on marginal land, where they just scrape by. When they have their 247,000 babies or whatever enormous amount they have, those babies disperse and some of them wind up settling down between fence posts just outside of the range. They don't survive... until the weather gets a little warmer.

The interchange of concepts between biology and economics is fascinating. One day I'd like to write a book on that history.


  1. I'd go with the idea of arachno-capitalist. It shows a lot of research potential.

  2. You're reading Principles of Population, aren't you?

    Malthus was a brilliant, brilliant man...


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