Jujube Tubes

I often get emails with requests for identifications of strange objects, and usually these are things that can be identified using my book.  Every once in a while, though, I’m treated to bizarre little mysteries from the other side of the world that bear little resemblance to anything I’ve come across in North America.  Sometimes I’m able to figure them out with a little Googling (as with the New Zealand Zigzag); sometimes other people pursue the mystery and fill me in (as with the square-mesh cocoon of Cyana meyricki).  With the mystery I’m about to present, the first option has failed me, so I’m hoping that someone out there either knows the answer or will stumble on it later and report back.

Judhajit Dasgupta noticed little white tubes attached to jujube (Ziziphus), an Indian shrub in the buckthorn family (Rhamnaceae).  He says the material of the tubes is a shell-like, hardened secretion.    He goes on:

I have examined the tubes under lens, there were no holes in the twigs near the site of attachment. Seems that the larvae concerned have only eaten the bark of the twig. Most of the tubes are placed at the nodes. The plant has completed flowering and has begun bearing fruits. No tubes are present on a nearby Jujube plant that is much younger and has not started bearing fruits. Some tubes have encircled the twig, some are attached only at a point. The diameter of the tubes are 1-2 mm, and length up to 7-8 mm. These are abandoned casings, so I shall look for them in coming seasons.

I don’t have much to say about these just yet, other than that I suspect they are made by some kind of moth larvae, but they don’t closely resemble the structures made by any tube/case-dwelling moth larvae I know about (e.g. Coleophoridae, Psychidae, Pyralidae). The annulated appearance of the cases in the close-up is interesting, and I wonder what close examination of the material sticking out of the tubes would reveal.  If these are in fact made by moth larvae, it would seem that one of the species in this list is responsible, but nothing there leaps out at me as a likely suspect (and I checked out and ruled out a few of the microleps).

So, anybody have a clue about this one?