As of August 23, 2004, this is the information I have.
Yesterday I spoke to one of the people on the BMC Identification Committee. She confirmed what others have told me. Even experts have problems deciding which is sensibilis, and which is bicolor. One will say it is bicolor while another will insist it is sensibilis. Only microscopic analysis by an expert can result in a positive ID. For us common folk, this is not practical.
Other mushroom foragers, information on the Internet, and even some guides, say that very few people are adversely effected by sensibilis. Most people experience no ill effect whatsoever. Of those that are effected, the result is stomach upset or diarrhea. In a small fraction of these that are effected, is it serious. Possibly these last actually have an allergic reaction.
So if you take normal precaution of not eating more then a spoonful of any new mushroom and waiting a few hours to see if you get some unpleasant sensations, there is no reason to try eating what you believe is bicolor. I was told by several people that they consider the bicolor on par in taste to Boletus edulis.
The primary test given in most guides is that sensibilis turns blue instantly while bicolor is slower. I don't know about you, but I have a problem telling what is "instant" as compared to what takes twice as long. How fast is twice as long as "instant"?? The color of the cap varies. The stem color varies. The stem shape and size varies. The speed of staining varies. For both bicolor and sensibilis. Last year I tried, several times, eating what I though was bicolor. I ate only a small cap or two. I had no ill effect. I remember one time, I boiled small specimens of what I believed to be bicolor. After boiling I noticed that some of the cap pores turned white while others remained yellow. To me that means that they were different species. I tried one cap of each. No ill effect. I personally do not care for Boletes. I think they are slimy and mushy, but I look forward to trying a bicolor and the KING.
I finish with a portion of a message from a Russian forager from the Boston area:
My experience is that the non-bicolor
mushrooms which are similar to
bicolor, when they are cut in pieces, bruise blue entirely and
even color the water in which they are put (the color of course disappears
in cooking). After exposure to air, the blue color becomes pale/grayish.
On the other hand, bicolor, although it may get a few
blue spots when handling, really retains yellow color of flesh
when cut (in cooking the blue disappears and they become
entirely yellow/brown). Also, the flesh of older bicolors
becomes soft. The stalks of non-bicolors tend to be tough
(especially in old ones), which is not the case for bicolors.
Also bicolor has a special (mildly sweet) taste which non-bicolors don't