On the question of stratigraphic distribution of fossil insects:
Someone wrote:
>>> I'm not current with the latest discoveries since then so can't comment
>>> much more than to say that it's always been thought that the evolutionary
>>> development of the insects (and other land-dwelling arthropoda) was closely
>>> tied to the evolutionary development of land plants (a whole new ecosystem
>>> to exploit!).
I noted:
>> In that light, it is a puzzle that there are so few Mesozoic insects, when
>> the first flowering plants to be preserved had entomophyllous pollen.
and you asked:
> On what basis are you saying that there are few Mesozoic insects? Few in
>terms of diversity? Few in terms of fossil localities? What exactly is the
>"puzzle" you're referring to?
Relatively few in diversity and locality, and especially in numbers of
specimens (abundance).
There are many fossil insects in Carboniferous deposits (giant cockroaches,
etc.), and many more (flies, beetles, ants, crickets, even butterfiles) in
Tertiary deposits. There are some (e.g. large dragonflies in the
Solenhofen limestone) in Mesozoic deposits, but not anything like what
would be expected if the flowering plants were co-evolving with insects.
This has been noted as a "problem" among angiosperm paleobotanists. I
remember talking to the entomologist that worked with N.F.Hughes at
Cambridge, who was eager to find any Cretaceous insects. That was 1980.
Some have been found, showing that the depositional environments were
capable of preserving insects. The paucity is a puzzle for those who
expect to trace the origins of entomopyllous (insect pollinated) plants in
the fossil record.
Karen