Re: Insects at K/T boundary

[bivalve@xxxxxxxxxxxx (David Campbell)]

>(1) Only a minority of temperate insects can hibernate. Most that
>overwinter do so by delayed maturation - i.e, by remaining dormant (or
>quiet, anyway) as larvae or pupae in sheletered habitats. Such as being
>underground, in rotting wood, trees, underwater, etc. They life cycles are
>such that the eggs are laid, and the larvae hatched at *just* the right
>time to pass through winter. Relatively few adults can hibernate as such
>(e.g., ladybirds, some social insects). So if a sudden cold snap hit
>mid-summer England, terrestrial insects would be as badly hit as everything
>else.
At least some caterpillars, when deprived of food, can pupate early.  The
adult moth is small but otherwise seems normal.  Additionally, many insects
go through multiple broods during the warmer months.  If emerging from the
dormant stage is a response to favorable environmental cues as soon as
possible [development takes some time!], multiple-brooded species could
readily survive unexpected cooling.  I don't know whether most broods can
delay maturation during unexpected cold weather, but I think this is pretty
much what is done artificially to mail live lepidopteran pupae.  Likewise,
does anyone know what cues the transition to overwintering stages in the
taxa that switch modes (e.g., aphids going from parthenogenesis to sexual
reproduction to produce durable eggs)?

David Campbell