Who among us has not been assaulted in one way or another by obnoxious bugs? That insistent mosquito late at night, or the stinging hornet, swarming ants, sand flies, fleas, ticks, and on and on — we humans are obviously and enormously affected by insects and other terrestrial arthropods in huge ways, from agriculture to health.

So it would be no surprise that bugs may have bugged life of the past as well, and that is the central claim of “What Bugged the Dinosaurs?: Insects, Disease, and Death in the Cretaceous,” a new book by George and Roberta Poinar that takes a new and novel look not only at past bugs, but at a nearly three-decade-long controversy: What killed the dinosaurs? The Poinars try to make the case that the insects did it.

For more than 200 years, there has been hot debate about the ultimate cause of the short-term intervals of widespread, cross-species death called mass extinctions. The dinosaur-killing event, called the KT extinction, was one of the five most devastating of more than 15 such events of the deep past. Those who study mass extinctions have long been divided into two camps. The “catastrophists” blame the extinctions on some sort of rapid, catastrophic event — such as global floods, extraterrestrial events including nearby supernova, or an asteroid impact on the Earth. Opposing this view have been the “gradualists,” who blame all that trauma on “normal” causes writ large: climate change, disease, sea-level change.

The gradualists held sway until 1980, when a team led by Berkeley’s Walter Alvarez presented compelling evidence that the KT event was caused by a 6-mile-wide asteroid (imagine Mt. Everest) falling from the sky at almost 10,000 miles an hour. This dramatic hypothesis was immediately challenged by paleontologists, on the grounds that the fossil record did not show the sudden pattern of extinction that such an event would necessarily cause, but by about 1985, many careful new studies showed that, indeed, the KT extinction was a rapid one, and the catastrophists appeared to have the advantage. By 1990, with the discovery of the giant crater in the Yucatan area of Mexico, the catastrophists took game, set, and match. Still, some paleontologists would not accept the evidence.

This willful ignorance is on full display in “What Bugged the Dinosaurs?” The Poinars trot out the now-discredited “evidence” of a non-catastrophic fossil record and, to replace the Alvarezes’ “Impact Hypothesis” for this extinction, they pose their own dramatic tale: The dinosaurs were “bugged out” of existence due to multiple effects of just too many verminous, disease-carrying, resource-munching, nasty terrestrial arthropods. Just bugged to death, in other words.

This hypothesis certainly deserves airing, and considerate scrutiny. But right out of the gate, the Poinars swing for the fences with hyperbolic overkill. Take this sentence: “One trembling ornithopod (a dinosaur?), with dry skin clinging to prominent ribs and vertebrae, staggered off to one side and began to vomit strands of bloodstained mucus filled with glistening, writhing roundworms.” Not only gross, this passage is pure imagination. Kind of a 10-year-old’s imagination at that. Of course, it’s not how visceral their prose is that bristles, but how speculative their claims. This is too bad: The Poinars’ scientific contributions for their “day” jobs (he as a zoologist, she as a researcher) have been a series of superb studies of insects in ancient amber, and it is this topic that best shines through in this book. The many incredible specimens that the Poinars have discovered in sap , made famous as the source of the dinosaur DNA in the various “Jurassic Park” movies, is brought into the narrative quite effectively. The book sparkles whenever the subject goes back to amber. But none of this relates a whit to the KT mass extinction.

All we really know from the amber studies is that there were lots of bugs back then, and we credit the Poinars as much as anyone that we now know the taxonomic identity of many of these ancient vermin. And what a rogues’ gallery of disgusting characters they throw at us: mosquitoes, black flies, biting midges, fleas and lice, horseflies and deerflies, all the way down in disgusting detail to ticks, mites, and parasitic worms supposedly working their havoc on poor saurian behemoths. (Yet what about all those underwater animals that went extinct too? Was there a huge cadre of underwater bugs as well?) Sadly, the book cannot make the case that these bugs actually affected the dinosaurs — because there is simply no such evidence.

Mr. Ward is a paleontologist and professor at the University of Washington. He is the author of “On Methuselah’s Trail,” “Under a Green Sky,” and “Rare Earth.”