Pupae vs. Chrysalis
Chris J. Durden
drdn at mail.utexas.edu
Mon Oct 22 12:28:48 EDT 2001
Ken,
I see we differ in details that are probably not significant to many
readers. See my comments below.
Primitive insects do not have larvae, just nymphs, which are little
versions of adults without mature sexual organs. Usually (there are
exceptions like dragonflies) these nymphs compete for food and living space
with adults.
Holometabolous insects avoid this competition between immature and
adult. They do this by the embryo hatching much earlier in its development,
before it has many of the adult structures. The primitive larva in moths
and panorpoid insects, in sawflies and neuropteroid insects is a
caterpillar. This caterpillar has functional abdominal legs retained from
the pre-hatchling embryo. The primitive larva in beetles, coleopteroid
insects is thysanuriform or campodeiform, reflecting a much more nymph-like
origin and separate origin of their holometaboly. The grub comes later as a
specialization towards a more confined existance as in weevils and wasps,
or a need for amoeba-like flexibility as in flies. The Holometabola are a
paraphyletic grade with two or three clades that have each evolved a larval
stage for similar reasons. The pupa is what is left of the nymph or
primitive insects. It is necessary to accommodate the drastic cellular
reorganization that takes place between larva and adult. There is a
pupa-like stage in some "hemimetabolous' Homoptera also among the scale
insects where larva-like nymphs retain juvenile characteristics into later
instars and a drastic reorganization is required to form the winged adult.
...........Chris
At 09:21 PM 10/21/2001 -0800, you wrote:
> I agree about sawflies and scorpionflies having caterpillars. What
>I don't agree on is _insects_ in general having caterpillars. Maggots and
>grubs are not caterpillars in my scheme of things...
No, but their ancestors were. I think of them as very specialized caterpillars.
> Larvae will do
>for all of them, of course. 'Boring and Too Long'
( I differ. I think it was too short. I despised the book because it left
out so many interesting families. I hold the authors' neglect of
systematics partially responsible for the dearth of insect systematists today.)
>has a definition of
>caterpillar that applies to sawflies and scorpionflies--but the authors
>showed no sign of extending it to maggots!
>
> And yes, butterflies have pupae (even though they may also be
>called chrysalids).
>
> I had never run across 'instar' applied to the egg stage, or to
>the pupa or adult of a holometabolous insect. Considering its meaning in
>Latin, I suppose it could be so used--but it's handy to have a special
>term for _larval_ stages.
>
> The problem with running the use of 'chrysalid' into the ground is
>that this is really more of a common-name type of thing, and may not fit
>the intricacies of taxonomy all that well. It is clear that some butter-
>flies have chrysalids. I would hestitate to claim that _all_ butterflies
>have them, especially when the definition of 'butterfly' is being expanded.
>But it seems clear enough to me that moths (or at least _most_ moths) do
>not have chrysalids--if by that you mean naked pupae (not to mention naked
>pupae with gold markings). And it also seems clear that non-lepidopterous
>insects don't have chrysalids, since the term was originally defined to
>apply to butterflies as far as I can tell.
In my pre-scientific days we always referred to the Cecropia or Goat Moth
chrysalis in it's cocoon. This may have been regional usage, but this usage
was present in southern England and eastern Ontario.
> My original teachers about lepidoptera were Remington and Clench
>(plus a lot of books). For what that's worth...
My original teachers about insects were my father, his professor (H. R.
Hewer of Imperial College), the great guys at the Dominion Museum of
Canada (Bousefield and others) and the Canadian National Collection (Jack
Martin, Gene Munroe, Dave Hardwick, Tom Freeman and many others). Remington
(whose influence a value much more now than I did at the time) and Clench
came much later. Influential too were Hutchinson, Petrunkevitch and Lanham.
> Ken
>
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