Phillip E. Johnson, a co-founder of the creationist intelligent design movement, said that the moths "do not sit on tree trunks", "moths had to be glued to the trunks" for pictures and that the experiments were "fraudulent" and a "scam." The intelligent design advocate Jonathan Wells wrote an essay on the subject, a shortened version of which appeared in the 24 May 1999 issue of "The Scientist", claiming that "In 25 years of fieldwork, C.A. Clarke and his colleagues found only one peppered moth on a tree trunk", and concluding that "The fact that peppered moths do not normally rest on tree trunks invalidates Kettlewell's experiments". Wells further wrote in 2000 "Icons of Evolution", in which he claims, "What the textbooks don't explain, however, is that biologists have known since the 1980s that the classical story has some serious flaws. The most serious is that peppered moths in the wild don't even rest on tree trunks. The textbook photographs, it turns out, have been staged." However, peppered moths do rest on tree trunks on occasion, and there is little difference between the 'staged' photos and 'unstaged' ones.