FNZ 9 - Protura (Insecta) - Systematics and Phylogeny
Tuxen, SL 1986. Protura (Insecta). Fauna of New Zealand 9, 52 pages.
(
ISSN 0111-5383 (print),
;
no.
09.
ISBN 0-477-06765-4 (print),
).
Published 24 Feb 1986
ZooBank: http://zoobank.org/References/6B017956-58FF-4405-9795-98BA1D6FE682
Systematics and Phylogeny
Protura are very small creatures, from less than 0.5 mm to 2 mm in length, white and softly sclerotised or harder and with a yellow tint, especially towards the hind end. Exceptionally they may be strongly sclerotised and red-brown in colour (Sinentomon from China, Korea, and Japan). The body is divided into three tagmata: a head with entognathous mouthparts, but without antennae or eyes; a three-segmented thorax with walking legs; and a twelve-segmented abdomen with rudimentary limb-appendages on the first three segments. This arangement of tagmata - head, three-segmented thorax, and abdomen of eleven or twelve segments - is characteristic of insects.
The lack of antennae has "caused" the forelegs to take over their sensory function, and they are furnished with sensory hairs (sensillae) the shape, number, and arrangement of which are of great systematic importance. On the supposed position of the eyes some organs called pseudoculi are situated; these may be homologous with the postantennal organs of Collembola and some Diplura. Spiracles are present on the mesothorax and metathorax in Eosentomoidea and Sinentomon, but the tracheae originating from each spiracle do not unite. The abdomen's full complement of eleven segments and a telson is not attained until maturation, a phenomenon (anamorphosis) that is exceptional among insects though usual in the myriapods. The external genitalia open behind the eleventh segment in both sexes, and are characteristically shaped. The spermatozoa are different from any other insect spermatozoon and very different in the two suborders of Protura (Baccetti et al. 1973).
The basic systematics of the group proposed by Tuxen (1964) is still that on which new additions are based. It is apparent in the key to suborders and families given on page 15.
Whether or not Protura are insects has long been, and is still, a subject of contention. In naming and erecting the order in 1907 Silvestri was of the opinion that they are insects, but in his admirable monograph of 1909 Berlese gave them the name Myrientomata, thus stressing their affinity to myriapods. The most recent view (and, incidentally, my own) is to regard them as a sister-group to Collembola within the subclass Entognatha (Hennig 1981); this in turn is a sister-group to Ectognatha, which comprises the Archaeognatha, Zygentoma (formerly Thysanura), and Pterygota (Tuxen 1980). As a sister-group to Collembola, which are known as fossils (Rhyniella) from Devonian strata, the Protura must be of the same antiquity at least. This fact I have used in my interpretation of their zoogeography (Tuxen 1978a).