Here's an opinion as to the cause:
"However, it is the thinking of one of the cell phone industry's former scientific hired guns that caught my attention. When George Carlo, M.D., the celebrated author of "Cell Phones: Invisible Hazards in the Wireless Age" and current chairman of the nonprofit Science and Public Policy Institute in Washington, D.C., weighs in with an opinion, we'd all be fools not to listen carefully.
On a recent conference call, Dr. Carlo laid the blame for the sudden demise (often within 72 hours) of entire bee colonies on the recent proliferation of electromagnetic waves (EMF). He cited the startling statistic that, at present, there are some 2.5 billion cell phone users around the world. While this (plus the explosive growth of cell phone towers) used to be the major concern, the problem has been significantly exacerbated by the recent introduction of satellite radio. Imagine being closeted in a confined environment filled with chain smokers; it would be impossible for you to get a breath of clean air. It is becoming equally difficult for you to avoid the now-measurable damage from EMF exposure.
Dr. Carlo commented that the constant electromagnetic background noise seems to disrupt intercellular communication within individual bees, such that many of them cannot find their way back to the hive. His conclusions are confirmed by a recent study conducted by three departments of Panjab University (India), which has found that cell phone towers - the dominant source of electromagnetic radiation in the city of Chandigarh - could well be the cause behind the mysterious disappearance of butterflies, some insects (like bees), and birds."
Swalker