Insects (and spiders) don't seem to fit into the classic fish,
amphibian, reptile line of evolution.  Is it possible that insects and
spiders evolved independently on land?, or can insect and spider
evolution be traced back to the sea like all other life forms?

Hi halejrb and thanks for another great question (we clearly share the
same interests!)

Your question is not unique !:
“Assuming mammals evolved from reptiles which evolved from amphibians
which evolved from fish, where did insects come from? Did insects
evolve separately on land or did they somehow come from the sea too?”
An answer is:
“ Insects evolved from a completely different line to terrestrial
vertebrates. They were established much earlier than the first
terrestrial vertebrates and invaded land well before the first
vertebrates. If you go back to the beginning, all life originated from
a watery environment. There is a natural progression from simple
organisms to complex ones, and at the same time along this
progression, different lines evolved separately in different
directions, insects being one of them, amphibians being another, etc.”
Unfortunately the link is broken to this site, however you can see it
in it’s cached form here:
http://216.239.39.100/search?q=cache:1fTdRDPntVQC:www.sci-ctr.edu.sg/ScienceNet/cat_life/cat_bio01435.html+%22insects+evolved+from%22&hl=en


If you are looking for some kind of ‘time line’
“Predators like the ladybird beetle and the praying mantid bite and
chew their prey while others (green lacewing larvae and big-eyed bugs)
use a sharp beak-like structure to suck fluid from their prey. The
feeding structures of these and all insects evolved from the chewing
mouthparts typical of insects that existed 400 million years ago.”
http://insected.arizona.edu/enforcers/background.html

and:

“We know that insects evolved from a crustacean-like ancestor at least
420 million years ago and that the most primitive forms were probably
much like today's silverfish.”
http://biology.usgs.gov/features/sistories/hasiotis.html

A really good search strategy is :
"insects evolved from "
://www.google.com/search?q=%22insects+evolved+from+%22&hl=en&lr=&as_qdr=all&start=30&sa=N


I hope this helps, and if you have any other questions regarding early
science and theories you are welcome back !

THX1138

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Request for Answer Clarification by halejrb-ga on 20 Jun 2002 06:42 PDT

OK, so insects evolved from crustaceans.  How about a short answer on
what spiders evolved from?

---

Clarification of Answer by thx1138-ga on 20 Jun 2002 08:37 PDT

Hi halejrb, Ok.....all about spider evolution.......

First did you know that person who studies spiders is called an 
arachnologist?

Spiders, like most animals have been around for a long time, between
300 and 400 million years, and originally evolved from crustaceans. 
The ability to spin webs was originally used to protect the spiders
eggs and not to catch prey, only later did they evolve that clever
trick. Today there are about 35,000 different species of spiders
living in most types of environments.
Here are some useful sites which will give you more details about
spider evolution.


“Very little is known about the early history of spiders. Unlike
vertebrates, arachnids have no internal skeleton which can easily be
fossilised. Some spiders have been, on rare occasions, fossilised in
tree sap, known as amber.”
*Available only in cache*
http://216.239.51.100/search?q=cache:5bFa_QvygC0C:www.tarantulas-online.co.uk/science/naturalhistory.html++%22spiders+evolved%22+&hl=pt


“The first spider evolved from crustacean like ancestors called
(Eurypterids) and the most ancient spider we know of is Paleocteniza
crassipes which walked and hunted on the earth in the Devonian period
of history more than 300 Million years ago (300 MYA). We would call
this the most primitive spider of all, and all its characteristics
would be described as primitive characteristics.”
http://www.earthlife.net/insects/webevolv.html
 

From the “THE JOURNAL OF ARACHNOLOGY” “A THEORY ON THE ORIGIN OF
SPIDERS AND THE PRIMITIVE FUNCTION OF SPIDER SILK”
“according to recent estimates approximately 35,000 species of spiders
exist”
*NOTE*  PDF Document
http://www.americanarachnology.org/JoA/JoA_v12_n1/arac_12_01_0021.pdf


“The first fossils clearly identifiable as spiders are from the
Devonian, 400 million years ago”
Also
“The evolution of the silk-spinning spider common ancestor involved
several steps: evolution of silk glands, spinneret morphology and web
making behaviors.”
http://www.swarthmore.edu/NatSci/sgilber1/bio111/ianweb/Spider/spider.html


You can listem to an explanation about spider evolution here:
http://www.earthnewsradio.org/99rafiles/1206994.ram


Were spiders created? ie. They didnīt evolve, but were made by ‘God’
http://www.icr.org/pubs/btg-a/btg-046a.htm



I hope this explains a little bit more about spider evolution, if it
was of help to you please donīt hesitate to rate the answer.

Thanks for your questions!

 THX1138


Search terms used:
"arachnologist"
://www.google.com/search?hl=pt&as_qdr=all&q=+%22arachnologist%22&btnG=Pesquisa+Google&lr=

"spider evolution"
://www.google.com/search?q=+%22spider+evolution%22+&hl=pt&lr=&ie=UTF-8&as_qdr=all&start=30&sa=N

Another great answer.  Google Answers is a really cool site!

Insects, spiders, crustations and anything else like those are all
from the same general area. They are actually evolved from very very
early plants, probally from Zooplankton, where as animals are from
phytoplankton. I hope that is all spelled right.

I'm too lazy to get proof, and I don't care about money ether so... I
just remember hearing this somewhere.