

Urbanization is supersizing spiders - bifrost
http://blogs.smithsonianmag.com/smartnews/2012/12/urbanization-is-supersizing-spiders/

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mjn
Spider size is a surprisingly interesting topic, with quite quick evolutionary
changes in both directions, and lots of interactions between spider size, web
size, prey size, etc.

Here's an excerpt from a book about some effects that influence the size of
orb-weaver spiders (internal citations omitted):

 _Spider size has evolved rapidly and diversely throughout the evolutionary
history of spiders, both in terms of absolute size and relative sexual size
dimorphism. In general, there seems to be a trend towards increased spider
body size, especially for females, across the phylogenetic tree. ... For orb
web spiders, the most common explanation is likely fecundity-based female
gigantism because clutch size, the most commonly used proxy for spider
fecundity, generally strongly correlates with female body size both intra- and
inter-specifically. ..._

 _[M]ight the function of orb webs also play a role in spider size evolution?
We believe the answer is yes. In general, orb web architecture determines the
type of prey intercepted and retained that could be consumed by the spider.
Thus, spider size evolution may occur under selection for how webs might fill
'empty niches'. For example, tiny anapid and mysmenids build orb webs that
capture insects ignored by larger orb-weavers, and theridiosomatids specialize
on mosquitoes that are too small to be relevant to the diets of large spiders
but also such specialized fliers that they are rarely captured by the webs of
other, less-specialized spiders. ... Similarly, the largest orb-weavers make
webs powerful enough to retain the largest insects, which are simply not
available to smaller spiders, and their webs can sometimes even subdue
vertebrate prey. Orb webs may place an upper limit on the maximum size
achievable by orb web spiders due to increases in the costs of producing webs
in larger spiders and due to differences in how the kinetic energy of insect
prey versus the stopping powers of orb webs scale with size._

Source:
[http://www.amazon.com/gp/product/0124159192/ref=as_li_ss_tl?...](http://www.amazon.com/gp/product/0124159192/ref=as_li_ss_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=0124159192&linkCode=as2&tag=kmjn-20),
pp. 225-226

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hartror
Non-Australians who click on linked article on huntsmans[1] should note these
are regular visitors in our homes. But as much as I love scaring foreigners
with our wild life (google dropbear) the ones you see day to day in urban
environments are generally 10cm across and happily cohabit with humans.

[1] [http://largestfastestsmartest.co.uk/largest-spiders-in-
austr...](http://largestfastestsmartest.co.uk/largest-spiders-in-australia-
huntsman-spider/)

~~~
ultimoo
Wow! That is very interesting.

In the US there are pretty comprehensive "pest-control" measures taken in
urban apartment complexes to ensure that there are absolutely no insects,
spiders or geckos indoors. I probably see a really tiny "house spider" (which
is probably a centimeter across in size) once or twice a year inside my
apartment.

So my question is it common to _not_ have pest control in OZ or is your house
the exception (since you are nature lover maybe)?

~~~
jfb
The thing about geckos and (as much as it pains me to admit it) spiders is
that they prey on much more noxious and difficult to control vermin,
particularly the mosquito. This is pretty useful when spiders are basically
harmless and _Anopheles_ the most dangerous animal in the world.

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r0h1n
A few years back, urbanization was also causing the breasts of Australian
women to grow larger :-|

[http://www.news.com.au/entertainment/fashion/dd-cup-
runneth-...](http://www.news.com.au/entertainment/fashion/dd-cup-runneth-over-
for-aussie-women/story-e6frfn7i-1225699623920)

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pbo
Small environments also have an influence over the body size of animals.
Surprisingly the change does not always occur in the same direction: see
_Insular Dwarfism_ and _Insular Gigantism_.

[1] [http://webecoist.momtastic.com/2010/08/09/insular-
dwarfism-1...](http://webecoist.momtastic.com/2010/08/09/insular-
dwarfism-12-species-that-evolved-to-be-small/)

[2] [http://webecoist.momtastic.com/2010/08/02/animal-
gigantism-1...](http://webecoist.momtastic.com/2010/08/02/animal-
gigantism-13-real-life-godzillas/)

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jfb
Speaking as a severe arachnophobe and a committed city dweller: great. Just
great.

