George Poinar Jr., a zoology professor at Oregon State University who wrote a commentary on the find of fossils of the giant insects by Chinese scientists, said they were probably 10 times the size of a flea you might find on the family dog.
"These were insects much larger than modern fleas and from the size of their proboscis we can tell they would have been mean," he said.
Poinar's commentary appeared in the same issue of Current Biology that reported the Chinese discovery.
"You wouldn't talk much about the good old days if you got bit by this insect," Poinar said in an OSU release Tuesday. "It would have felt about like a hypodermic needle going in -- a flea shot, if not a flu shot. We can be thankful our modern fleas are not nearly this big."
The soft-bodied, flea-like insects found in fossil form in Inner Mongolia may be the evolutionary ancestors of modern fleas but are more likely a separate and now extinct lineage, he said.
"These are really well-preserved fossils that give us another glimpse of life into the really distant past, the Cretaceous and Jurassic," Poinar said.