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.
Vein terminology
Longitudinal veins
The Comstock and Needham system attributes different names to the veins on an insect's wing. From the
anterior
Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
(leading) edge of the wing towards the
posterior (rear), the major
longitudinal veins are named:
*''costa'' C, meaning ''rib''
*''subcosta'' Sc, meaning ''below the rib''
*''radius'' R, in analogy with a bone in the forearm, the
radius
In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...
*''media'' M, meaning ''middle''
*''cubitus'' Cu, meaning ''elbow''
*''anal veins'' A, in reference to its posterior location
Apart from the costal and the anal veins, each vein can be branched, in which case the branches are numbered from anterior to posterior. For example, the two branches of the subcostal vein will be called Sc
1 and Sc
2.
The radius typically branches once near the base, producing anteriorly the R
1 and posteriorly the ''radial sector'' Rs. The radial sector may fork twice.
The media may also fork twice, therefore having four branches reaching the wing margin.
According to the Comstock–Needham system, the cubitus forks once, producing the cubital veins Cu
1 and Cu
2.
According to some other authorities, Cu
1 may fork again, producing the Cu
1a and Cu
1b.
As there are several anal veins, they are called A1, A2, and so on. They are usually unforked.
Crossveins
Crossveins link the longitudinal veins, and are named accordingly (for example, the medio-cubital crossvein is termed m-cu). Some crossveins have their own name, like the
humeral crossvein h and the sectoral crossvein s.
Cell terminology
The cells are named after the vein on the anterior side; for instance, the cell between Sc
2 and R
1 is called Sc
2.
In the case where two cells are separated by a crossvein but have the same anterior longitudinal vein, they should have the same name. To avoid this, they are attributed a number. For example, the R
1 cell is divided in two by the radial cross vein: the basal cell is termed "first R
1", and the distal cell "second R
1".
If a cell is bordered anteriorly by a forking vein, such as R
2 and R
3, the cell is named after the posterior vein, in this case R
3.
References
*Comstock, J.H. & Needham, J.G. (1898) The wings of Insects. IX The Venation of the Wings of Hymenoptera. ''The American Naturalist'', 32:413-424.
*
External links
North–Carolina state University course on insect wings
{{DEFAULTSORT:Comstock-Needham system
Insect anatomy
Biological classification