The sinister buzz of insects fills the soundtrack of "Picnic at Hanging Rock," while people warn one another of venomous snakes. Evil is all about, and into it merrily skips a bevy of old-fashioned schoolgirls on an outing.

That something will attack them is certain. What it is, we never find out. As in "The Last Wave," director Peter Weir is juxtaposing European civilization against the Australian terrain, and frightening us by warning that civilization is weaker.

It's an effete civilization, where green English lawns have been forced onto rough, dry ground, and the etiquette of stiff collars and corsets makes no allowances for tropical heat. The girls go for an outing to a volcanic rock formation, and some disappear.

The insects and the snakes are false leads, and so are trances and wounds. Watches stop at the vaguely mystical time of 12. It is Saint Valentine's Day: Is love responsible?

One lovely girl is always represented by a swan. Those who disappear have lost some of their clothes, but we are constantly assured that the girls were left "intact."

A deserted orphan yearns for her brother, passing him unknowingly all the while, as he also wonders about her. The headmistress (Rachel Roberts) establishes the character of a heartless disciplinarian, but her fate turns out to be self-sacrifice.

Mysterious statements are uttered and echoed: "A surprising number of human beings are without purpose, although it is probable they are performing some function unknown to them," an "Everything begins and ends at exactly the right time and place." Were the girls who make these remarks already possessed by pedantic spirits, or is this what their parents are paying to have put into their heads?

What, at any rate, is in Weir's head?

He has attempted Impressionism, to give his impression of Australia as battleground between Nature and Conqueror. That may be why he has chosen the period and the characters he did. With their parasols and fluttering white dresses and peach-like skin, they recall Impressionist paintings, sometimes in a quite lovely way.

Purely visual cinema was accomplished successfully in "Days of Heaven," where there is no story line to speak of, but people and nature are made memorably vivid through the moving picture."Picnic at Hanging Rock" is not up to that level visually, because it occasionally slips into the hair-color advertisement school of slow-motion beauty. But even the attempt is marred: Looking for game clues would spoil any painting, but having to look and not being able to find them is worse.