Insect Larva

Ernst Hippe · Post by **Ernst Hippe** » Sat Aug 22, 2009 12:26 pm

Hallo,
my first posting is a question. Can somebody identify this larva:

Achr.Plan 2,5x. Canon A95. Polarized light with aux. object.

Ernst Hippe

rjlittlefield · Post by **rjlittlefield** » Sat Aug 22, 2009 1:39 pm

Ernst, welcome aboard!

This is a damselfly nymph. For comparison, see http://images.google.com/images?hl=en&q ... ly%20nymph.

--Rik

rjlittlefield · Post by **rjlittlefield** » Sat Aug 22, 2009 1:44 pm

I am curious about the notations "L = 5,2 mm" and "+960 nm".

Am I correct in thinking that the first one describes the length of the larva's body (without tails), and the second describes the size of a pixel?

--Rik

bernhardinho · Post by **bernhardinho** » Sat Aug 22, 2009 3:48 pm

rjlittlefield wrote:I am curious about the notations "L = 5,2 mm" and "+960 nm".

Am I correct in thinking that the first one describes the length of the larva's body (without tails), and the second describes the size of a pixel?

--Rik

Hi Rik

I hope Ernst won't mind if I clarify this. He is well known over here for his home-made retarders. So here he applied 960nm retardation. The other one is the length indeed!

Cheers

Bernhard

rjlittlefield · Post by **rjlittlefield** » Sat Aug 22, 2009 4:26 pm

Bernhard, thanks for the clarification. I'm certainly glad I asked!

--Rik

Ernst Hippe · Post by **Ernst Hippe** » Sun Aug 23, 2009 1:21 am

Hi Rik,

thanks for your welcome and the quick & complete answer, especially the link!
Bernhard, thanks for "first aid". In this case, L is the length including tails.

Ernst

Ernst Hippe · Post by **Ernst Hippe** » Sun Aug 23, 2009 9:15 am

It may be of interest, that the animal lost his tails completely after the recent moult.
Here is the stripped-off skin to show the tails better (including an ostracode in 2 positions during the stack):

Ernst

rjlittlefield · Post by **rjlittlefield** » Sun Aug 23, 2009 9:28 am

Interesting. I had this happen to some when I was a kid, growing them in an aquarium. Losing the tails was not typical for the species in the wild, but they lived fine afterward. I was surprised by this because the tails are gills, used for oxygen exchange. So I wrote to a university asking about it. The reply said that the gills were responsible for only about half the total oxygen exchange (I forget the exact number), with the rest occurring through the cuticle of the body. So the nymphs would be fine as long as the water contained enough oxygen. I don't recall if the writer said anything about what might trigger loss of the gills.

--Rik

Ernst Hippe · Post by **Ernst Hippe** » Mon Aug 24, 2009 2:38 am

As far as I see the tails were not lost after the moult, but were not re-devellopped before. Perhaps there is not enough oxygen in the petri dish. The nymph seems to be rather weak now.

bernhardinho · Post by **bernhardinho** » Mon Aug 24, 2009 1:39 pm

rjlittlefield wrote:Ernst, welcome aboard!

This is a damselfly nymph.
--Rik

Hi Rik

just out of interest to hear what you'd have to say to our discussion in the german forum. Our problem is that on Ernst' pic everthing apart from the tail looks indeed like a damselfly nymph. BUT the three-fold tail showing no gills at all looks much more like a mayfly larva.

http://images.google.de/images?q=mayfly ... =de&tab=wi

another fine mess you've gotten us into

Any idea to clarify that question??

Bernhard

rjlittlefield · Post by **rjlittlefield** » Mon Aug 24, 2009 2:24 pm

Gills on a damselfly nymph can be very flat and are aligned vertically.

When I saw the first picture, I assumed the gills are seen "on edge", same as in the picture at http://www.bumblebee.org/invertebrates/Odonata1.htm.

The followup picture, showing cast skin, suggests that the tails are not very wide in any case. But I think the picture shows clearly the central shaft of the gill, with a thinner flat portion surrounding it.

I did not even consider mayfly nymph, just from general appearance. Now that I do think about, I don't think that's right. It would be a very odd mayfly nymph to show no trace of gills along the sides of the abdomen.

--Rik

Ernst Hippe · Post by **Ernst Hippe** » Tue Aug 25, 2009 8:50 am

Rick,
I think I maintain with the specification "damselfly larva/nymph": no side gills, tails as described. Possibly Lestes spec.
Thanks for an interesting discussion!
Ernst

Planapo · Post by **Planapo** » Tue Aug 25, 2009 9:36 am

Ernst,
On your damselfly larva you should find that the labium has a very characteristic form (and function): It's a prey catching device that can be thrust out quickly in order to fullfill its task. In German it's called "Fangmaske". In its resting position it lies folded back on the underside of the larva's head. You could try to swing it out with a fine needle or forceps, if you've still got the specimen.

--Betty

Ernst Hippe · Post by **Ernst Hippe** » Tue Aug 25, 2009 1:00 pm

Betty,
incidently I just got a picture of the ventral head side, so you see the labium at least frontally. Darkfield without pol.:

The larva did'nt survive, so I'll try to take it laterally too.

rjlittlefield · Post by **rjlittlefield** » Tue Aug 25, 2009 2:09 pm

Classic damselfly.

The way these things catch prey is startling to say the least. I tried to find a video online, but in quick search I couldn't find anything. There is a still image at http://www.mdfrc.org.au/bugguide/diagrams/odonata.htm that may give you some idea of how it works.

--Rik

Insect Larva

Insect Larva

Damselfly nymph

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