Class Insecta

[Ken Kinman]

Dear All,
     Only have a week left, so I wanted to get one more subject in for
possible comments.  Back when I was compiling my 1994 classification, I
struggled with two alternatives for Class Insecta (my Insectea):
     The two best choices were both reflected in the Encyclopaedia
Britannica (1975 Edition and later printings).  I chose the broader
treatment presented in the article on Insecta, which made it equivalent to
Hexapoda (thus including the entognaths).
    However, in the Encyclopaedia Britannica's article on Apterygota, Keith
Wise of New Zealand proposed that Insecta be restricted to the ectognathous
forms.  Now that Atelocerata (hexapods and myriapods) has become a doubtful
clade, I am more inclined to the possibility that entognaths could have
evolved separately from ectgnathous Insecta either in parallel or even
convergently from different crustacean ancestors.
     Therefore, I plan to remove the 3 orders of entognaths from my Class
Insectea.  The basal insect order will thus be Microcoryphida (the
bristletails, which are monocondylic) as sister group to the rest of the
insects (clade Dicondylia).
     The only question which now remains is whether to treat entognaths as a
single Class, or treat them as two separate Classes (elliplurans and
diplurans).  And in this context, I am even considering the possibility that
the entognaths (springtails, proturans, and forktails) could have perhaps
evolved such mouthparts from an ectognathous form (such as bristletails).
That might seem an unusual viewpoint (ectognathy as derived), but that is
one possibility I have not yet definitely rejected.
     But I guess perhaps only Devonian fossils of "forktails" could really
give us the information we need to make a definitive decision on these and
related questions.  So I'm still mulling over the possibilities for
entognaths (one class or two), but feel that restricting insects to the
ectognaths is the best way to go.  Comments are welcome.
      -------- Cheers,
                    Ken Kinman

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