BOOK REVIEW : Examining Nature in Insect Songs : CRICKETS AND KATYDIDS: Concerts and Solos <i> by Vincent G. Dethier</i> ; Harvard University Press; $18.95; 140 pages.

To catch the tinkling ground Cricket, Prof. Vincent Dethier drags his net, trawler-like, through fallen leaves. He discards twigs, sprigs, seeds, cobwebs and the odd caterpillar and keeps the tiny reddish-brown tinkler. To catch the shield-bearer katydid, on the other hand, he mixes beer and molasses in a pot.

I knew I was well and truly netted when I found myself making my way through a key at the end of Dethier’s unlikely and inveigling calendar of insect song. “Series of soft buzzes, Tsikk, Tsikk, Tsikk: sprinkled locust.” And: “Never five clicks between buzzes, incessant wheezing day and night, tse-tse-tse-psee: slender meadow grasshopper.”

As for the molasses and beer, I suspect I was well and truly potted right at the start. Dethier quotes Charles d’Orleans--”Time hath laid his mantle by/Of wind and rain and icy chill/And dons a rich embroidery . . . .”--to suggest his theme. The week-by-week appearance and extinguishing of different insect sounds marks the passage from spring to fall as surely as do turns in foliage, flowers and human hearts. Listening is another way to examine nature and to contemplate ourselves.

Dethier is a professor of zoology, and clearly he has spent his thousands of hours with microscope, preserving fluid and diagrams of wing-cases. He is one of those scientists, however, who has never forgotten the link between the explicit and the immanent. Wonder leads to dissection, or he would not be an entomologist; dissection leads to wonder, or he would not be a writer.

And “Crickets and Katydids” would not be for the likes of me, to whom they are all bugs, although from now on, I will think of them as orthopterans. It means straight-winged and includes locusts and grasshoppers, as well as cockroaches, though these do not appear in the book because they are mute.

It was chance as well as temperament that allowed Dethier to develop his contemplative side. As a student he was hired for the summer by G. W. Pierce, a physics professor who had decided to study insects for their acoustics. Dethier’s job was to find the insects in the fields and woods around Pierce’s laboratory cabin in Franklin, N.H.

To do that, he had to listen. To listen, he had to remain very still, preferably reclining. A young man lying on his back in a New Hampshire meadow may be a scientist, but he will look remarkably like a poet, and he will see and hear like one too. “Under what other circumstances,” Dethier writes, “could a person lie on his back staring at the marching cumulus and be working?”

Dethier had to train his ear to differentiate among the sounds variously produced by wing-cases scraping wings or wings scraping hind legs. Chirps, trills, tinkles, crackles and buzzes may stand out from each other--at least for him--but the difference between one kind of ground cricket and another may simply be the number of clicks in the trill.

Fortunately, there was an order in which the species made their seasonal entrances: Field crickets first, then ground crickets, then locusts and grasshoppers, then katydids and, finally, tree crickets. It gave the student time to learn.

We get appealing glimpses of the young man at work and otherwise--it’s hard to distinguish. Seeking the Carolina cricket at midnight, he is dragged out of the local graveyard by the sheriff, who takes him for a vandal. He mingles with the townspeople in the evening to see the train go by. By this time, we know he hears the approaching whistle as an outsize insect call.

He spends a day climbing Mt. Washington after the gladiator grasshopper. Except for a few clicks in the middle, its song is exactly like that of the common meadow grasshopper down in Franklin.

Does the difference matter? Is it worth climbing a mountain for? Nature finds it important, he tells us. Otherwise, a gladiator would hop through the tall grass only to find a common meadow grasshopper with whom no mating was possible, a matter of genetic incompatibility.

Dethier has good things to say about katydids and locusts, although they are rather monotonous. But his heart goes to the crickets’ exuberant chirping and to their rounded heads. The most delicate is the snowy tree cricket’s “sound of moonlight, if that could be heard.”

In a foreword, poet A. R. Ammons praises the professor for “the sound he makes,” adding: “We learn from his sounds what kind of person, capable of this kind of interest and care, is attending to our minds.” Dethier can be flowery, but there is a live orthopteran behind each flower. And sometimes the words surge as piercingly as a tree cricket’s. He stands in a hazy dusk and hears the landscape stretch out.

“In the grass at one’s feet, the ground crickets trill the here while the chirp of a laggard field cricket marks the farther boundary of the field. In the forest beyond, muted but unmistakable, the song of a hermit thrust channels one’s aural perspective to the purple hills. There, as far as the ear can focus, is silence, the remote, the unperceived. In that remoteness is peace.”