Goofs

The plane carrying the A-Bomb is referred to as a B-52 Superfortress, but the stock footage used is of a B-36 Peacemaker.

At the beginning of the movie, two teens are making out. Then, the female looks up and recoils in horror, intimating that she's seen one of the giant locusts. However, much later, Dr. Wainright says that before they attack, grasshoppers let out an ear-piercing screech. Yet, there was no screech before the teens were attacked. Even though they had the radio on, the screeches heard later in the film are deafening and, thus, the teens should have heard it.

During the first locust encounter with the soldiers, a scene of a soldier falling down on one knee and firing his rifle at the locusts is reused a few scenes later.

During the battle for Chicago, whenever a grasshopper appears directly in front of troops, soldiers turn to their right and shoot away from it.

The rear view mirror on Audrey's car appears and disappears depending on where and when the scene was filmed. It is usually there (at the top of the windshield) when she pulls in front of the military command post and gone when she's driving on the highway or entering the Ludlow area.

The pilot and co-pilot of the B-52 are not in flight suits.

The sound used for the giant grasshoppers is actually the sound that the Common True Katydid makes.

Even though in the movie the giant bugs are called locust and sometimes grasshoppers, locust are grasshoppers that have turn into locust when grasshoppers swarm together. The ones shown in the movie are all male Differential Grasshoppers (Melanoplus Differentialis). These grasshoppers never swarm together.

When the locust attacks the soldier at Observation Post #3 on the roof, you hear him screaming through the radio that is in the Emergency Lab, but the handset of the radio is just dangling on the radio. These handsets require a button to be pushed to talk.

Some editions (the MST3K episode at the very least) omit a short scene about 8 minutes in where Audrey tries to sneak some photographs of Ludlow and is caught by an officer who confiscates her camera. With this scene removed, there is an apparent continuity error when she later tells Col. Sturgeon that her camera was confiscated when she was there, then shows up at the checkpoint again to retrieve it.

In at least one of the shots of grasshoppers climbing a building, they can be seen walking on the sky background, revealing that the "building" they're climbing is actually a postcard.

When Wainwright is trying to locate the correct frequency to lure the locust into water, in the background by the file cabinet is a mannequin dressed as a soldier. The mannequin disappears and then reappears while Wainwright is telling the general that they have discovered the frequency.

When Ed and Audrey report to the Col. Ed says about the giants "these are 8 feet tall, some even bigger" yet there was only one at the destroyed warehouse.

In the brief shot of the grasshoppers supposedly being lured into the lake, there are clearly almost as many walking away from the water as there are walking towards it.

When at the destroyed warehouse Ed says that the ground is "completely barren" but they are kneeling among grass.

It seems unlikely that, with all the towns and cities in front of Chicago being overrun and destroyed that so many people would still not be evacuated from Chicago and its immediate suburbs.

After being turned away at the checkpoint Audrey drives away to sneak some photos. When she stops her car you can see a pair of feet walking in the reflection on her door.

About 21 minutes into the movie. While Dr. Ed Wainwright, Frank the deaf mute, and Audrey are talking by the giant tomatoes, you can see a person walking around behind the set. You can see them through the wooden slats.

There are no mountains in central Illinois.

Peter Graves tells Morris Ankrum that the grasshoppers become inactive at night, when the temperature goes below 68 degrees. Yet, the beginning of the movie implies that the grain storage site and the town of Ludlow were destroyed overnight.

It's never explained how the number of grasshoppers increased from a few hundred to endless thousands.

The sound boom shadow appears in at least four shots: across the detectives' and cop's bodies as they examine the girl's bloody sweater, on the National Guard office's inside door as Audrey enters the building for the first time, across Captain Barton's helmet as he and Audrey are talking in her car upon returning from Ludlow, and across a piece of electronic equipment as Ed and a soldier examine Major Everett's body after the locust attack.

Dr. Wainwright says that the giant grasshoppers failed to develop wings. It's obvious, even at a glimpse, that the real grasshoppers used in matte shots do indeed have wings.