Giant insects??

[William Tivol]

Dear Hauk,

[snip]
: I would like say that I have absolutely NO education or
: experience with biology, so please dont laugh to my question.

	It's actually a very reasonable question.

:     I know that insects and arachnids could be unbelievable big in
: prehistoric times. 

	Probably not, for the reasons given below.

: I know that these creatures are prevented from
: growing bigger than today due to limited amounts of oxygen in the air.

	Not true.  However, such creatures must distribute O2 to their
tissues without the aid of a vascular system, so they cannot be so large
that diffusion won't do the job.  Other physiological imperatves, e.g.,
mass increases as the cube of a characteristic length; whereas, muscle
strength increases as the square, also set limits to size.  It should be
noted, however, that spiders exist in a size range about two orders of
magnitude, so under proper conditions, it might be possible to evolve
fleas the size of tarantulas--a scary thought.

: I also know that some of these insects have been altered by virtually no
: genetic evolution ever since then.

	They have evolved at the same rate as other clades (a general
term for groups of organisms--species, genera, clssses, etc.).  The
present day insects have different alleles from insects which lived
millions of years ago, even though their outward appearances are very
similar.

:     What if those days environment (oxygen, moist, temperature, light,
: etc.) was simulated in a huge tank or something? (The oxygen level and
: temperature could even be raised above the "30 000 000 BC" standard. And
: the availability of healthy food should also been taken care of, maybe
: spiced up by steroids or other interesting chemicals). Would insects and
: arachnids grow up to be the same gigantic beasts as they once where????
: (Up to 50 cm.)

	Probably the availability of food (and the absence of "more highly
evolved" competitors) are the limiting factors.  I haven't done the math,
but 50 cm, or larger, could be possible--after all, lobsters are in the 
same phylum.  I wouldn't think this size to be "gigantic".

: I guess that some boring realities makes the answer a "NO way!". 

	I find the realities to be fascinating.  The ways in which the
laws of physics and the interactions among the members of an ecological
system limit the parameters of size are beautiful and complex.

: But
: anyway, I would appreciate a comment from anyone who knows a bit about
: these things.                                                ^^^

	Glad to oblige.
				Yours,
				Bill Tivol