H Ludi Tyler wrote:
Apparently the breeding nest of carpenter ants needs moisture for the eggs, but they create satellite nests which do not require moisture. So to locate the queen may require finding where there is moisture or rotten wood.
More details: http://www.extension.umn.edu/distribution/housingandclothing/DK1015.html

They use a special type of pear, though I'm pretty sure you have to use a certain type of pear for wine, too. 