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Desert curiosity

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Desert curiosity

Postby Bob Burd » Sun Nov 18, 2012 9:39 pm

I came across these sand sculptures a number of times in the Mojave, and wondered what their purpose is. They appear to be made of sand, probably by some insect (ants?), covering the branches of some low scrubby plants. Though brittle to the hand, they appear to be somewhat durable, outlasting the life of the plants they encase. Anyone know what these are?

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Re: Desert curiosity

Postby Scott M. » Sun Nov 18, 2012 11:54 pm

Bob, we can wait for a real botanist to chime in but I'll offer a far reach of an idea. There is an insect that creates a sticky substance called lac that coats the branches of the creosote bush (Larrea tridentata). I wonder if wind blown sand adheres to the lac on the branches and creates this coating. The lac is resinous and hardens over time. Scott
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Re: Desert curiosity

Postby lcarreau » Mon Nov 19, 2012 1:33 am

I'm not the botanist, but ANTS also play an integral role ... "One way to tell if a creosote bush has a scale infestation is to look for the presence of ants. While these ants are found in large numbers on the bush, they are not there for the bush itself but for the lac scales.

These scales excrete a sticky and sweet substance called honeydew. This substance is sought out by ant colonies and, once the ants have found a supply, they will defend the lac scales from other insects while harvesting the honeydew for their colony ..."
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Re: Desert curiosity

Postby Scott » Mon Nov 19, 2012 3:03 am

Looks like a termite nest.
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Re: Desert curiosity

Postby Bob Burd » Mon Nov 19, 2012 5:39 am

Scott wrote:Looks like a termite nest.


Good call. I did a search on 'desert termites' and similar pictures come up. I would never have guessed termites could be found in the desert...
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Re: Desert curiosity

Postby LongLost » Wed Nov 21, 2012 2:14 am

Interesting, never seen that. Not that I spend much time in the southern deserts though.

And the call is correct. Edmund Jaeger in The California Deserts, 4th edition (1965), p. 45 states the following:

"Very curious are the queer, earthen shelter-galleries built over dead desert shrubs by the Arizona desert termite (Amitermes arizonensis). Often the interior wood is almost entirely eaten away, leaving fragile earthen tubes which crumble to dust upon being touched. The insects are most active after summer rains, and at such times almost all the dead shrubs over wide areas may appear like plants 'spattered thick with mud' "

The species in question is now referred to as Amitermes wheeleri I believe.
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Re: Desert curiosity

Postby MoapaPk » Wed Nov 21, 2012 2:05 pm

Termites can't deal with dryness; they often build sand structures over exposed wood so they can harvest the stuff without being roasted by the sun.

A few inches below the surface of the desert, the humidity approaches 100%. I've found termites, even in "cold deserts." Down by S New Mexico, they make up a large fraction of the underground biomass. In the "cold deserts," often you will be able to lift a dead woody bush right out of the ground with ease; once the plant dies and stops making protective sap, termites (and carpenter ants) chew it off at the roots.
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