Tuesday, March 8, 2011

Ambrosia Beetle- Part II

The Ambrosia Beetles (Xylosandrus crassiusculus) that we discussed  in last week's blog is only a tenth of an inch long.  Unlike the beetles causing Thousand Cankers which bore just under the bark, the Ambrosia Beetle bores tiny tunnels deep into the wood and carries a fungus which eats into the xylem.  The beetle and its larvae then eat the fungal mycelium and clusters of its spores, their only source of food.   The relationship is symbiotic in that the fungus is totally dependent on the beetle to spread its spores and reproduce.

How does the fungus make the trip?  It travels in the beetle's mycangium, specialized structures for the transport of symbiotic fungus.  Many beetles with this feeding strategy can eat other things or even digest wood along with their fungal meal.  Some types of beetle mycangium are simple pits on the surface of their body where the fungi hangs on seemingly by chance.  Since the Ambrosia beetle won't survive without its fungal friend, it goes to greater lengths to make sure it survives the trip.

Ambrosia Beetle's mycangium have deep and complicated pouches.  They may have glands which secrete substances to support and feed the fungus.  Some even have fine setae (hairs) to scrape the fungal spores and mycelia from the tunnel walls into the pouch.

The spring and summer flights of the beetle can be monitored by the use of traps.*  The bait is ethanol which is normally extruded in tiny amounts by sick or dying trees.  The Ambrosia beetles are lured in to have a drink at their equivalent of the neighborhood bar and succumb to the soapy water at the bottom.   You might say that they get "really bagged".

*  More on traps at this site.
The Ambrosia Beetles article has detailed information about this creature.

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