Thanks Peter, Yes, they are definitely hollow. They are all split vertically, and the material has vertical ridges on it which makes me think it isn’t an egg shell. I am pretty sure the little yellow balls inside the husk are pollen grains, they are stuck inside and onto the surface of many of them.
In the 90’s I worked at NSW Ag at BCRI Rydalmere, and if it still existed I could have wandered upstairs to visit my entomology friends, and taken it on a short stroll to the electron microscope unit, or across campus to AQIS. We often got envelopes full of carpet fluff sent in by the public to search for mystery critters and would have a little chuckle at their expense usually. The demise of that institute upsets me to this day.
I will look up where to send a sample and hope they don’t laugh at me 
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