Monthly Mystery #16: Tubes on Silver Raisin

Yesterday a friend forwarded me this photo that had been posted to the “Southern Africa Butterflies, Bugs, Bees and other small things” Facebook group to see if I had a clue what it was.  At first, I didn’t.  The photographer, Lee Gutteridge, wrote:

Here is one more that has baffled me lately, taken in the Klaserie. These tiny white calcium shells are common on the Silver raisin bushes (Grewia monticola) and i have it on pretty good authority that it is a type of aphid which is responsible for creating the shell. However, this little guy was running around on one of them…is he related to the shell above him? it looks like a psyllid. can anyone shed any light on this for me please? 

LeeGutteridge3

I contacted Lee for permission to post his photo here, and he sent me a few additional ones:

LeeGutteridge2

LeeGutteridge1-001

I agree that the bug in the first photo appears to be a psyllid nymph, and in contemplating whether it could be related to the structures, I remembered the two Australian psyllid species that have shown up on eucalyptus in California.  They live in shelters called “lerps,” made from their own waxy secretions, as seen here and here.

But Lee had described these things as “calcium shells,” so evidently the substance isn’t waxy.  As I was starting to put this post together, I suddenly remembered those jujube tubes from India, which turned out to be made by froghopper nymphs.  I just did a little reading to refresh my memory about these things, and I came across this 2001 paper by Andy Hamilton, which notes:

These tubes have been said to be “calcareous” with “not less than 75% calcium carbonate” (Ratte 1884) although modern studies show that they are mainly made of mucofibrils (Marshall 1965), which are thick, gelatinous compounds that dry to a rocklike hardness. Mucofibrils are produced by excretory ducts of the lower intestine called Malpighian tubules.

Looking at the illustrations of the different tube types on the third page of that paper, I’m pretty well convinced that these South African objects are something similar, and that the psyllid-like nymph just happened to be wandering by.  So it seems that I may have accidentally solved this mystery before posting it, although I still have no clue what species does this on Grewia monticola.

As an interesting side note, Lee mentioned that he is busy with an insect/invertebrate track and sign book for his region. I look forward to seeing it, and I commend Lee for being able to focus on things like this while having to keep an eye out for lions and leopards at the same time!

About Charley Eiseman

I am a freelance naturalist, endlessly fascinated by the interconnections of all the living and nonliving things around me. I am the lead author of Tracks & Sign of Insects and Other Invertebrates (Stackpole Books, 2010), and continue to collect photographs and information on this subject. These days I am especially drawn to galls, leaf mines, and other plant-insect interactions.
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One Response to Monthly Mystery #16: Tubes on Silver Raisin

  1. Pingback: An Update and a Fancy Moth | BugTracks

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