Neoptera

This group of winged insects appeared in the earliest Late Carboniferous (early Bashkirian) and subsequently radiated into every imaginable terrestrial and freshwater niche. Features of the Neoptera (discussed earlier, and briefly reiterated here) include wing flexion via special muscles attached to the third axillary sclerite (Figure 4.6), the formation of a median plate in the wing base, the radial vein never forking from the wing base, and the development of a gonoplac (i.e., the third "valvula").

Why should this group have been so successful among the flying insects? The ability to flex the wings over the abdomen when at rest is much more significant than it might at first appear, and it is a remarkable quirk of nature that a few tiny muscles attached to a minute sclerite should be one of the main reasons for the great success of insects. Wings are vital means of dispersal and thus require protection; they need to be stored when not in use and to minimize damage while the insect is moving amidst leaves, under bark or rocks, or in other tight spaces. The wings themselves can also serve to protect the abdomen, which is the function of leathery forewings, or tegmina, in roaches and some orthopteridans, and the entirely sclerotized earwig tegmina and beetle elytra. The ability to adeptly control the wings when not aerial was certainly a major innovation among the flying insects, as is shown by the fact that when fossil neopterans appeared, they quickly outnumbered paleopterous insects.

Some of the earliest neopteran insects include members of the Carboniferous family Paoliidae (Figure 7.1). Paoliids were rare, large insects that have at times been placed in their own order, Protoptera (e.g., Sharov, 1966). The group is characterized by numerous primitive features, and they actually lacked any derived traits (at least none observable in preserved specimens). This family is very likely a stem group to all other Neoptera. Ten genera and 12 species are presently recorded from the early Pennsylvanian of Europe and North America (e.g., Smith, 1871; Handlirsch, 1906a,b, 1919; Laurentiaux, 1950; Kukalov√°, 1958; Brauckmann, 1984, 1991;

Laurentiaux-Vieira and Laurentiaux, 1986; Maples, 1989). The antennae were long and filiform, and the legs were unmodified, slender, and had five-segmented tarsi. Unfortunately, the paoliids are poorly understood, with few body characters known; fortunately, however, the wings are preserved. These insects had relatively broad, homonomous wings with rich crossvenation that formed an archedictyon, and the hind wing lacked an anal fan. The absence of an anal fan in most non-neopteran lineages suggests that this is a primitive trait for Neoptera and that this feature may indeed support the monophyly of Polyneoptera (with several, independent reversals therein). Paranotal lobes were not present in paoliids, and the occurrence of these structures among some "Protorthoptera" families, particularly those allied to the Plecoptera, may be a derived trait for those lineages as well (and convergent with the paranotal lobes in Palaeo-dictyoptera and Geroptera). Alternatively, but a less parsimonious explanation, is that paranotal lobes are primitive for all pterygotes (and homologous to the "protolobes" of Zygen-toma), in which case the loss of such lobes would have occurred independently in the Ephemeroptera lineage (including Lithoneura), in Holodonata, in Dicliptera + Diaphanopterodea + Eumegasecoptera + Protohymenoptera, in Paoliidae, and in Eumetabola and frequently among polyneopterans.

Neoptera is generally divided into three major lineages: Polyneoptera, Paraneoptera, and Holometabola, the latter two being sister groups and each definitively monophyletic, while strong support for a polyneopteran group is elusive.

The Polyneoptera, under one concept or another, have traditionally gone by the name of Paurometabola (exclusive of several orders), Orthopteroidea, or simply the orthopteroid insects. This is a disparate group of generalized and specialized unlikely relatives, and indeed, the group is ill-defined and may not be natural. Some superordinal groups appear well supported, particularly the Plecopterida, Orthopterida, and Dictyoptera (discussed later), while the orders Dermaptera, Grylloblattodea, and Mantophasmatodea are v I

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