Wednesday, October 22, 2014

White Micrathena

Micrathena micrata - REK
M. gracilis - Wikimedia
Driving through the woods we encountered the usual spiny orb weaver spiders (Micrathena gracilis) we wrote about in July.  One however looked a lot smaller and turned out to be a white micrathena - Micrathena micrata.  Its abdomen had a different shape and it has only two black spines, unlike the six spines of M. gracilis seen on the right.

It was originally described by Nicholas Marcellus Hentz (1797-1856) in 1850.  He was a French-American scholar, a professor of modern languages, and an arachnophile.  For you arachnophobes, the 'phile' means someone who 'loves, likes or is attracted to' instead of fearing.  In his spare time, Hentz described 124 species of spiders, species that were overlooked by other new world observers at the time who were studying more charismatic arthropods such as beetles and lepidoptera.

Incredible as it sounds today, all this study, writing and classification, eventually published by others, was a hobby, no pay and little recognition.  Most of the science at that time was what we now call "citizen science."  While we how have trained scientists to collect, codify and make sense of what is published, much of this came originally from passionate amateurs.


Without wading into the morass of the formal naming and renaming of species, M. micrata is Latin for 'wearing a turban.Hentz wrote that "The abdomen viewed from above resembles a bishop's mitre."  As you can see above, he made a very good point.

The competitive exclusion principle states that "No two species can occupy the same niche in the same environment for a long time."  How do these two species seem to exist together?  While M. micrata is more common to the north, their range overlaps in southern Missouri.

They coexist side by side in some geographical areas and their niche is not identical.  M. micrata is only a quarter inch long, half the size of M. gracilis.  Its web is lower and more dense that M. gracilis, aimed at finding smaller prey flying low above the lower forest floor.



The next time I walk into a face full of white micrathena's web, I will try to remember that it was just looking for tiny flying creatures and I am just its 'bycatch.'

You can download The Spiders of the United States (1875) by Edward Burgess for free at this site.  It is an interesting look at the original descriptions of spiders in the mid-eighteenth century.

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