Archedictyon

Archedictyon from Greek Arche meaning first, original, ancient, primitive, or most basic  Word Info: "arche-"and dictyo- meaning net or netlike  Word Info: dictyo- (plural = archedictya) is the name of a hypothetical scheme of wing venation of the common ancestor of all winged insects. Jarmila Kukalová. Revisional Study of the Order Palaeodictyoptera in the Upper Carboniferous Shales of Commentry, France. Part III. Psyche 77:1-44, 1970.

Description
The nature of the archedictyon is an important in the taxonomic classification of the large, primitive Palaeozoic insects known as Palaeodictyoptera. It was used for this purpose as early as 1854. Jarmila Kukalová. "Revisional study of the Order Palaeodictyoptera in the Upper Carboniferous shales of Commentry, France" Part III. Psyche 77:1-44, 1970. 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 [of] the wings of many of the most ancient insect fossils; the complex network of irregular veinlets between the veins in the outer [three-quarters] of both wings, including the anal lobe. Museum of Natural History

According to a 1999 paper on the evolution of flght in Palaeoptera the cross veins of some Palaeodictyoptera may be an adaptive feature.  Cambridge Philosophical Society: Flight adaptations in Palaeozoic Palaeoptera (Insecta)

Structure
500px|center|thumb|Venation of insect wings, based on the Comstock–Needham system

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. Archedictyon

The "Comstock-Needham system" designed by two entomologists describes these veins and their branches:

Costa (C): the leading edge of the wing
Subcosta (Sc): the second longitudinal vein (behind the costa), typically unbranched
Radius (R): the third longitudinal vein, one to five branches reach the wing margin
Media (M): the fourth longitudinal vein, one to four branches reach the wing margin
Cubitus (Cu): fifth longitudinal vein, one to three branches reach the wing margin
Anal veins (A1, A2, A3): the unbranched veins behind the cubitus. North Carolina State University

Crossveins are named based on their relative position to the more prominent longitudinal veins:

C-SC crossveins run between the costa and subcosta
R crossveins run between adjacent branches of the radius
R-M crossveins run between the radius and media
M-CU crossveins run between the media and cubitus.

 Living species 
In extant insects, the term implies a retention of primitive characteristics but not necessarily a simplicity of form.  Modern insects with wings to which the term archedictyon has been applied include the termite Mastotermes darwiniensis from Australia and the praying mantis Orthodera novaezealandiae. Purkayastha, M. 1999, Orthodera novaezealandiae, University of Michigan Animal Diversity Web. Accessed July 27, 2008 from New Zealand.

The term is also used in the discussion of phasmids. Then it refers to a network of non-directional veins in the costal region of the wing or in the elytron.  Glossary of terms used to describe phasmids

Bibliography
 "An enigmatic Palaeozoic stem-group: Paoliida: designation of new taxa from the Upper Carboniferous of the Czech Republic"  (pdf file)

References

Category:Insects