[Taxacom] Proventrum or prosternum?

[David Redei]

I agree with Mike's comment but I want to add some details.

In the *pterothoracic *segments of several higher insects, most notably in
all Endopterygota (but with considerable differences in some orders), the
sternum is deeply invaginated along the midline of the segment (the
invagination is usually marked by a median longitudinal groove externally),
and a sclerite derived from subcoxal and pleural elements is found in
ventral position anteriad to and between the coxal insertions. Although
this latter sclerite is occasionally called "sternite" by descriptive
taxonomists, it is more proper to call it "ventrite" (mesoventrite,
metaventrite) to stress that it is not homologous with the primary sternite
found e.g. in Plecoptera.

The ventral *prothoracic* sclerite differs from the ventral pterothoracic
sclerites in several respects, among others in the lack of median
longitudinal groove. In spite of the differences this sclerite potentially
is also composed at least partly of subcoxal and/or pleural elements,
although as far as I am aware the details are not fully explored yet. If
yes, it would be more accurate to call it as a ventrite (proventrite) as
well. Most authors on beetles currently adopt the traditional terminology
(prosternum), following them until the question is settled certainly will
not cause any confusion in taxonomic papers.

With best regards, David Redei

On 28 December 2015 at 04:25, Michael A. Ivie <mivie at montana.edu> wrote:

> As is so often the case, it depends.  It depends on the Order you are
> talking about, and in the Coleoptera even what group.
>
> Prosternum is a strict morphological term that implicitly suggests a
> hypothesis of morphological homology with the original sternum of the
> prothoracic segment in the primitive insect.
>
> Proventrite is a positional term with no such implication of morphological
> homology.  It is just the sclerotized area between and anterior to the
> procoxae, no mater what original sclerites are incorporated.  So, the usage
> can be either, depending on the information content intended by the author,
> but they are not the same thing.  When you choose, you should known which
> you mean, and be able to justify it.
>