Diptera.info

Posted by Tony T on 18-03-2010 21:52

Anyone know what these yellow discs are?
I don't believe they are spiracles.

Edited by Tony T on 18-03-2010 21:53

Posted by Eric Fisher on 19-03-2010 06:43

Tony,

Those structures are "abdominal plaques" and are found in many suborders of nematocerous and orthorraphous brachycerous Diptera (but not in the Cyclorrhapha). They are thought to be "scars" where tendons and muscles attached to the cuticle during the pupal stage. They have also been called "sensory pits" in earlier years (incorrectly, as no sensory function has been found for these structures). The best study I know of is: Stoffolano, J.G., N.E. Woodley, A. Borkent and L.R.S. Yin. 1988. Ultrastructural studies of the abdominal plaques of some Diptera. Annals of the Entomological Society of America 81:503-510.

Eric

Posted by Tony T on 19-03-2010 14:45

Thanks Eric.
I had never heard of these. The Manual of NA Diptera does not mention them and Idema did not include them in his drawing of a female Sciara.

Posted by Eric Fisher on 19-03-2010 18:03

You're most welcome Tony. I just noticed that the new "Manual of Central American Diptera" mentions them in the "Adult Morphology and Terminology" chapter (no doubt because that 1988 paper had appeared in the interim). Interestingly, the figure used is the Rhamphomyia abdomen (no. 101, pg. 42) from the NA Manual, where some plaques are shown but not annotated. (That incredible artist, Ralph Idema, never missed a significant detail!). Many figures from MNAD are reused in MCAD -- especially for the morphology chapter. BTW, your sciarid photos are beauts!

Edited by Eric Fisher on 19-03-2010 18:05