The idea of neural processing and signalling happening <i>outside</i> what we generally think of as the nervous system has me wondering about how oders are processed by insects.<p>E.O. Wilson has written of a "chemical grammar" of ants, and the relative characteristics of, say, danger or alarm signals, versus food or "friend" signals.<p>An alarm signal should propogate quickly, be easily recognised, and <i>dissipate</i> relatively quickly (no need in being alarmed long after the danger has passed). There's little concern that it be identifiable to other species. Small, light, volatile chemicals serve this.<p>A food or "friend" identifier should be persistent, fairly durable, and <i>not</i> be the same between different species (for various reasons). Larger, heavier, and less-volatile chemicals serve this.<p>The thought's occurred to me that with simple neurological systems, insects may have adapted neurochemicals to serve as exosomatic message transmitters (or maybe I'm getting this backwards and neurotransmitters have evolved from simpler chemical signalling). Which would make the "hive mind" a reality in mire than just metaphor.<p>Extending the concept, trees and plants with their massive surface areas make for a potentially very capable chemical emission and detection system. It was only after thinking that the branches (and roots) of a tree resemble the dendritic structures of neurons that I caught myself remembering that "dentrite" means "tree". So, yeah, doh!<p>It also suggests that whilst individual <i>trees</i> don't think, <i>forests</i> might....<p>Rampant speculation, but I'll toss it out there.