In January 1986 I arrived at the University of York in northern England as an NSF–sponsored post–doctoral fellow to conduct a field experiment involving insects on bracken. One day in February, while waiting to begin the real work in the summer, John Lawton stopped me in the hallway and asked me if I thought it would be possible to use the parasitoid–host literature to examine patterns in the number of parasitoid species that individual herbivore species support, in much the same way as he and others had analyzed herbivore species richness patterns on plants. My response was immediate and self–assured: No! Everyone knows that the records are too fragmented and the data too piecemeal and biased to have any chance of finding any meaningful results. But after returning to my office and thinking it over for a while, I decided that it could not hurt to try, particularly since the Yorkshire winter is ideal for this type of research. The following day I made the first of what was to become many trips to the library to search the literature.

Looking back, I suspect that my response to John's question may have been overly pessimistic. The initial analysis of the parasitoids of British insects revealed a number of potentially interesting patterns, but it raised far more questions than it answered. A follow–up analysis of North American patterns of parasitoid diversity produced results surprisingly similar to those found in Britain, but, again, there were nagging doubts about what they really meant.