[Odonata-l] Strange Larval Behavior

[Bob Glotzhober]

I have been trying to rear an anisopteran larva taken from Big Darby
Creek, just a little west of Columbus. I have not tried to force it
through a key as I'm hesitant to manipulate too much while it is alive
and earlier instar exuvia have not survived well prior to me finding
them floating in the container. However, I believe it is likely
Nasiaeschna pentacantha, the Cyrano Darner. When collected it had two
light spots on the dorsal surface of the abdomen segments 6 and 7.
Andrew Boose also had one - more mature than mine, and his has emerged
in a normal fashion. His maintained the two dorsal spots through to its
final instar, mine has lost them and is uniformly dark brown (last time
noted with twin spots was about F3, last October). When I collected it
(Sept.6, 07) it was an estimated F5 larvae and 9mm long. It has molted
five times, and I believe it is a final instar with a head width of
7.2mm, total length of 28.5mm and a hind wing sheath length of 4.8mm. It
is a female larva. The ID is very tentative for now - but that is not
the question I have.

 

Mine has been in what I believe to be the FO instar stage since June
5th. I have a branch in the container that it can climb up on. It eats
well, though this has slowed down during the last couple of weeks. For
at least a month or longer it has been crawling part way up the stick.
(Sorry, I've been so busy with other projects, I failed to record when
this behavior started.) I am accustomed to FO larvae doing this for a
week or two prior to molt, leaving (initially) the last half of the
body, or (toward the end) the tip of the abdomen in the water. This one
has been observed for long periods totally out of the water. I was
concerned it was dead, but it readily moves to avoid me if I touch it.
More problematic, not only does it sit totally out of the water, but
sometimes it head-first, and sometimes it sits totally out of the water
and upside down  -- i.e. head pointing toward the water. I've never seen
this behavior before, nor recall reading anything like this.

 

So I have this upside down, out of water behavior in addition to a very
prolonged period of time after initiation of out-of-water behavior and
it has still not molted into the adult. Any comments, references or
thoughts are appreciated. Just what is going on here?

 

====================

Robert C. Glotzhober             614/ 298-2054

Senior Curator, Natural History         bglotzhober at ohiohistory.org

Ohio Historical Society         Fax: 614/ 297-2546

1982 Velma Avenue

Columbus, Ohio  43211-2497

 

Visit the website of the Ohio Historical Society at:

  www.ohiohistory.org and check out our online collections catalog.

See or purchase Dragonflies and Damselflies of Ohio or the Cedar Bog
Symposium II at OHS's new E-Store:  http://www.ohiohistorystore.com/ 

Visit the Ohio Odonata website at:
http://www.marietta.edu/~odonata/index.html

 

 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailweb.ups.edu/pipermail/odonata-l/attachments/20080805/9b502092/attachment.html