[Odonata-l] headless dragonflies

[Richard Rowe]

John and Sue Gregoire <khmo at att.net> wrote:
> This is a fascinating subject. My 2 cents:
>  
> In 2006 we had a rather large number of Celthemis elisa emerge from 
> one of our ponds. It was a very rainy year, so my field notes are 
> interesting. During a 2 day period of heavy rain, both day and night, 
> hundreds emerged each day. They made their maiden flight into the 
> Goldenrods around the pond OK but probably ran into problems with wet 
> wings sticking to wet vegetation and starved to death. That species 
> emergence was much lower this year.
>  
> As to death: how can you tell when a dragonfly is actually dead? 
> We once placed a headless Anax on our bench to see what would happen. 
> His wings fluttered AND he continued to defecate for three days. 
> Surely, without a head, he was "dead", but the autonomic reflexes were 
> still activated.
>  
> Sue G.
remember dragonflies, like many of the hemimetabolous insects, have a 
distributed nervous system with high levels of 'delegation'.  So thorax 
activities are controlled by the three thoracic ganglia and the abdomen 
by the abdominal ganglia; and with no instructions from up front these 
will continue to go about maintenance activity and local comfort 
movements until the metabolism runs down.  Headless larvae 'leak', but 
the thin neck of adults often seals,

Richard

-- 
Dr Richard Rowe
Zoology & Tropical Ecology
School of Marine & Tropical Biology
James Cook University
Townsville 4811
AUSTRALIA

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