Archedictyon (from Greek Arche meaning first, original, ancient, primitive, or most basic [1] and dictyo- meaning net or netlike, [2] plural "archedictya") is a name given to a hypothetical scheme of wing venation proposed for the common ancestor of all winged insects. [3]
The nature of the archedictyon is an important consideration in the taxonomic classification of the large, primitive Palaeozoic insects known as Palaeodictyoptera and was used by Adolphe-Théodore Brongniart for this purpose as early as 1854. [4] A National Museum of Natural History database for the study of ants, wasps, bees and termites describes the archedictyon as:
...the primitive original vein network characterizing the wings of many of the most ancient insect fossils (T-B, after Needham; Mackerras, in CSIRO); in Mastotermitidae and Hodotermitidae (Isoptera), the complex network or reticulum of irregular veinlets between the veins in the apical 3 quarters of both wings, including the anal lobe (Emerson). [5]
According to a 1999 scientific paper about the evolution of flight in Palaeozoic Palaeoptera, although the archedictyon of some Palaeodictyoptera have long been believed to be generalized plesiomorphic reticulation from which true cross veins developed through evolution, these may actually be an adaptive feature. [6]
The archedictyon is believed to have contained between six and eight longitudinal veins, but current understanding of the design is based on a combination of fossil data and speculation. [7]
The "Comstock-Needham system" designed by entomologists John Henry Comstock and George Needham describes these veins and their branches: [8]
Crossveins are named based on their relative position to the more prominent longitudinal veins:
The hypothetical primitive wing venation pattern is often used as a basis for describing the pattern in modern insects.[ citation needed ]
In extant insects, the term implies a retention of primitive characteristics but not necessarily a simplicity of design in comparison to the veinous network of other modern insect wings. Contemporary insects with wings to which the term archedictyon has been applied include the termite Mastotermes darwiniensis from Australia (illustration)[ infringing link? ] and the praying mantis Orthodera novaezealandiae [9] from New Zealand.
The term is also used in the discussion of phasmids and in such case refers to:
A network of non-directional veins in the costal region of the wing or in the elytron. It is these veins which make the elytron and costal region of the hindwing thicker and stiffer than the anal region of the hindwing. [10]
The Palaeodictyoptera are an extinct order of medium-sized to very large, primitive Palaeozoic paleopterous insects. They are informative about the evolution of wings in insects.
Meganisoptera is an extinct order of very large to gigantic insects, informally called griffinflies. The order was formerly named Protodonata, the "proto-Odonata", for their similar appearance and supposed relation to modern Odonata. They range in Palaeozoic times. Though most were only slightly larger than modern dragonflies, the order includes the largest known insect species, such as the late Carboniferous Meganeura monyi and the even larger early Permian Meganeuropsis permiana, with wingspans of up to 71 centimetres (28 in).
The most recent understanding of the evolution of insects is based on studies of the following branches of science: molecular biology, insect morphology, paleontology, insect taxonomy, evolution, embryology, bioinformatics and scientific computing. It is estimated that the class of insects originated on Earth about 480 million years ago, in the Ordovician, at about the same time terrestrial plants appeared. Insects are thought to have evolved from a group of crustaceans. The first insects were landbound, but about 400 million years ago in the Devonian period one lineage of insects evolved flight, the first animals to do so. The oldest insect fossil has been proposed to be Rhyniognatha hirsti, estimated to be 400 million years old, but the insect identity of the fossil has been contested. Global climate conditions changed several times during the history of Earth, and along with it the diversity of insects. The Pterygotes underwent a major radiation in the Carboniferous while the Endopterygota underwent another major radiation in the Permian.
Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments, and the two pairs are often referred to as the forewings and hindwings, respectively, though a few insects lack hindwings, even rudiments. The wings are strengthened by a number of longitudinal veins, which often have cross-connections that form closed "cells" in the membrane. The patterns resulting from the fusion and cross-connection of the wing veins are often diagnostic for different evolutionary lineages and can be used for identification to the family or even genus level in many orders of insects.
This glossary of entomology describes terms used in the formal study of insect species by entomologists.
The Anisopodidae are a small cosmopolitan family of gnat-like flies known as wood gnats or window-gnats, with 154 described extant species in 15 genera, and several described fossil taxa. Some species are saprophagous or fungivorous. They are mostly small to medium-sized flies, except the genera Olbiogaster and Lobogaster, which are large with bizarrely spatulated abdomens. Their phylogenetic placement is controversial. They have been proposed to be the sister group to the higher flies, the Brachycera. Some authors consider this group to be four distinct families – Anisopodidae, Mycetobiidae, Olbiogastridae, and Valeseguyidae.
Diastatidae are a family of flies in the order Diptera. They are encountered primarily in the Holarctic Region, but several species are found in the Oriental, Neotropical and Australasian regions. Members of the family number over 20 described species in three genera. There is an additional fossil genus.
Pallopteridae is a family of flies. The various species are collectively called flutter-wing flies, trembling-wing, or waving-wing flies, because of the striking vibration of the wings in many species. Over 70 species in about 15 genera are found in the temperate regions of the Northern and Southern Hemispheres.
The Dixidae are a family of aquatic nematoceran flies (Diptera). The larvae live in unpolluted, standing fresh waters, just beneath the surface film, usually amongst marginal aquatic vegetation. They are found in all continents except Antarctica.
"Roachoids", also known as "Roachids" or "Blattoids" are members of the stem group of Dictyoptera. They generally resemble cockroaches, but most members, unlike modern dictyopterans, have generally long external ovipositors, and are thought not to have laid ootheca like modern dictyopterans.
Orthodera novaezealandiae, known as the New Zealand mantis or the New Zealand praying mantis, is a species of praying mantis which is, as both the scientific name and common names suggest, indigenous and endemic to New Zealand.
Insect morphology is the study and description of the physical form of insects. The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical features separate insects from other arthropods: they have a body divided into three regions, have three pairs of legs, and mouthparts located outside of the head capsule. It is this position of the mouthparts which divides them from their closest relatives, the non-insect hexapods, which includes Protura, Diplura, and Collembola.
The Comstock–Needham system is a naming system for insect wing veins, devised by John Comstock and George Needham in 1898. It was an important step in showing the homology of all insect wings. This system was based on Needham's pretracheation theory that was later discredited by Frederic Charles Fraser in 1938.
Dipteran morphology differs in some significant ways from the broader morphology of insects. The Diptera is a very large and diverse order of mostly small to medium-sized insects. They have prominent compound eyes on a mobile head, and one pair of functional, membraneous wings, which are attached to a complex mesothorax. The second pair of wings, on the metathorax, are reduced to halteres. The order's fundamental peculiarity is its remarkable specialization in terms of wing shape and the morpho-anatomical adaptation of the thorax – features which lend particular agility to its flying forms. The filiform, stylate or aristate antennae correlate with the Nematocera, Brachycera and Cyclorrhapha taxa respectively. It displays substantial morphological uniformity in lower taxa, especially at the level of genus or species. The configuration of integumental bristles is of fundamental importance in their taxonomy, as is wing venation. It displays a complete metamorphosis, or holometabolous development. The larvae are legless, and have head capsules with mandibulate mouthparts in the Nematocera. The larvae of "higher flies" (Brachycera) are however headless and wormlike, and display only three instars. Pupae are obtect in the Nematocera, or coarcate in Brachycera.
The Tarsophlebiidae is an extinct family of medium-sized fossil odonates from the Upper Jurassic and Lower Cretaceous period of Eurasia. They are either the most basal member of the damsel-dragonfly grade ("anisozygopteres") within the stem group of Anisoptera, or the sister group of all Recent odonates. They are characterized by the basally open discoidal cell in both pairs of wings, very long legs, paddle-shaped male cerci, and a hypertrophied ovipositor in females.
Elektrithone is an extinct genus of lacewing in the moth lacewings family Ithonidae. The genus is solely known from an Eocene fossil forewing found in Europe. At the times of description the genus was composed of a single species, Elektrithone expectata.
Odonata are insects with an incomplete metamorphosis (hemimetabolous). The aquatic larva or nymph hatches from an egg, and develops through eight to seventeen instars before leaving the water and emerging as the winged adult or imago.
Palaeopsychops is an extinct genus of lacewing in the moth lacewings family Ithonidae. The genus is known from Early Eocene fossils found in Europe, and North America and is composed of ten species. The ten species can be informally separated into two species groups based on veination of the forewings, the "European" and "North American" groups. When first described, the genus was placed in the family Psychopsidae, but later was moved to Polystoechotidae, which itself is now considered a subgroup of the moth lacewings.
Mazothairos is an extinct genus of very large insect from the Carboniferous period. It was a member of the order Palaeodictyoptera. Although it is only known from very fragmentary remains from a single fossil, it is estimated to have had a wingspan of about 56 centimeters (22 in), making it one of the largest-known insects, only being rivaled in size by the largest members of the order Meganisoptera, such as Meganeura and Meganeuropsis.
Polystoechotites is an extinct parataxon of lacewings in the moth lacewing family Ithonidae. The taxon is a collective group for fossil polystechotid giant lacewing species whose genus affiliation is uncertain, but which are distinct enough to identify as segregate species. Polystoechotites species are known from Eocene fossils found in North America and is composed of four named species Polystoechotites barksdalae, Polystoechotites falcatus, Polystoechotites lewisi, and Polystoechotites piperatus, plus two unnamed species. Three of the described species are known from fossils recovered from the Eocene Okanagan Highlands of Washington State, while the fourth is from Colorado.
{{cite web}}: CS1 maint: archived copy as title (link) Cambridge Philosophical Society: Flight adaptations in Palaeozoic Palaeoptera (Insecta)