Blood Flow in Odonata Wings -

One of a series of Web pages by Roy J. Beckemeyer devoted to ASPECTS OF INSECT BIOLOGY.

Last updated 5 February, 2002

This information is taken from the work of John W. Arnold, an entomologist with the Canada Department of Agriculture, who wrote "Blood circulation in insect wings" (Memoir No. 38 of the Entomological Society of Canada) in 1964.  He studied blood flow in the wings of a wide variety of insects, including the following Odonata:  Enallagma ebrium, Ischnura veritcallis, Lestes unguiculatus, Cordulia sp., and Sympetrum sp.  He noted that there "were no major differences in wing circulation among the species or between the fore and hind wings of individuals" for the Odonata.   Nomenclature for veins is based on the Comstock-Needham system.

The wing veins of insects generally are pathways for the flow of haemolymph (blood), for the passage of tracheae (which provide air exchange), and for the routing of nerves.  Wings are living tissue, and they become dry and brittle if blood circulation ceases.  

In the general case, the "route and mechanism of blood circulation in the wings ... are fundamentally alike in all species and in all forms of wings.  In general, blood from the lateral intermuscular spaces of the thorax enters the wing at the humeral angle, flows distally to the wing apex through the large anterior veins and moves en route through cross veins toward the posterior margin.  It returns to the body via the posterior veins..."

The picture below shows the flow pattern overlaid on a scanned image of the fore wing of a male Sympetrum corruptum.

There are some unique aspects to the flow pattern in the Odonata, tied to the peculiar features of the Odonata veins: the arculus, nodus, and pterostigma.  Flow from the body to the wing tip, i.e. distal flow, is called afferent flow by Arnold.  The returning flow is called efferent flow.  The nodus, which couples the afferent veins, diverts a portion of the blood from the afferent to efferent streams, "thus providing a short route for the blood through the wings."  Similarly, the arculus allows some of the afferent flow in the combined Radius-Media vein (which contains the greatest volume of blood afferently) to flow back toward the body, joining the efferent streams from the medial veins and the Radial Sector (RS).  The pterostigma is "a box-like sinus" which accepts blood from the surrounding veins "but does not significantly alter the circulation." 

Arnold notes  that the arculus and nodus together "may be responsible for the noticeable reduction in strength of the blood current in the wing extremities and for the tendency for those areas to become dry and to fragment in the late stages of adult life."  The figure at right shows the tattered wings of a female Sympetrum corruptum in October, after a long and apparently difficult flight season.

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