(Note the first: spoilers ahead, blah blah blah…)
Note the second: The episode list at the Wikipedia article lists "The Lost Dorgyte" as the next episode after "Mekkor", and "Destroyer Ants" after that; while the Big Cartoon Database lists "Destroyer Ants" as following "Mekkor". Since "Destroyer Ants" has no prologue (usual for the first episode in a program), I consider the BCDB entry to be the more accurate.)
The skies over Amzot are rent with savage lightning!
One rock formation in particular seems to bear the brunt of the electrical attack...
and begins to glow. A lightning bolt also blasts an opening in the rock...
…which is revealed to be hollow! The ceiling of the cavern is covered in large, green egg-shaped nodules, one of which begins to glow…
…and fall to the ground. It is indeed an egg, and hatches a huge, three-eyed ant!
More eggs are energized, and hatch out more ants…
…which march out of the cave, on a mission of destruction!
At the treehouse, Igoo growls uneasily.
"Do you hear that, too, Igoo?" Tara asks. "We'd better go have a look."
Tara and Igoo cross a deep chasm between two cliff on a log bridge. "I still hear it, but I don't see anything," Tara comments. "Whatever it is, I don't like it!"
Tara is suddenly confronted by a giant ant! "IGOO!"
Roaring in challenge, Igoo rushes (well, as quickly as a giant rock ape can) to Tara's rescue.
The ant has grabbed Tara up in its front legs, but drops her when it sees several tons of angry rock ape charging at it!
Igoo bears the ant down to the ground, but the ant manages to kick Igoo off…
…sending him crashing into a nearby cliffside while Tara looks on anxiously. "Watch out, Igoo!" The ant tries to press its advantage against a stunned Igoo, who tries to shake off the effects of the ant's attack. "Get up, Igoo, get up!!" Tara cries.
Igoo takes advantage of his proximity to a pile of large, flat stones; he picks one up and clobbers the ant with it.
He then picks the body of the ant up and flings it over the edge of a cliff.
The other ants gather around the body of their fallen comrade; then, as if vowing revenge, they swarm up over the cliff edge.
"More ants!" exclaims Tara. "Thousands of them! Igoo! Igoo!"
Igoo moves forward, ready to take them on single-handedly; but Tara warns him off that foolhardy deed. "Back, Igoo! Back!" Igoo reluctantly backs off.
Pointing back to the bridge they just crossed, Tara explains, "We've got to get back to the other side!" Tara and Igoo rush across the log bridge to the (relative) safety of the other side.
As the ants gather ominously on the farther cliff, Igoo bellows belligerently from his side. "Igoo! You've got to hold them, until I get help!" says Tara.
Igoo breaks a branch off the log…
and as the ants scurry across one by one, Igoo bats them away!
"If it's what you say, Tara," says Zandor, on Zok's back with Tara behind him, "unless they're stopped, they'll destroy all life on this planet!
"Dorno, stay close!" Dorno rides atop Tundro, with Gloop and Gleep behind him. "Yes, Zandor!"
"Look! There's Igoo!" Tara points from her vantage point on Zok's back. Igoo is still swatting ants; then gets a better idea.
Grabbing the entire log, he dislodges it, sending a number of ants crashing to the bottom.
"He's destroyed the bridge!" exclaims Tara. "Yes," Zandor responds, "but I'm afraid that won't stop them. Look!!" Zandor points to a disturbing development…
…as the ants climb up each other…
…forming towers that fall forward…
...bridging the gap between the cliff with their own bodies, as Igoo watches in consternation.
Once again, Igoo has to be warned away (this time by Zandor) from engaging the marauding ants. But once Igoo is clear of the area…
"NOW, Zok!" Zandor shouts.
And Zok unleashes his eye- and tail-beams against the ant-bridges, collapsing them down to join their fellow ants at the bottom of the ravine.
The gathered Herculoids survey the situation. "Great! That stopped them," observes Dorno.
"Once they start on the march, nothing stops them!" says Zandor. "Look!"
Once again, the ants form their own bridges across the chasm; if nothing else, they're certainly persistent. "It didn't stop them!" says Dorno.
"What are we going to do?" asks Tara.
Zandor points to a distant canyon. "Our only hope is that they will keep marching toward the canyon between those bluffs!"
"But what if they don't?" asks Dorno. "I've got an idea," responds Zandor. "Evrybody head for the bluffs except Igoo. Now hurry! They're coming fast!"
Turning to the rock ape: "Igoo, I have another job for you!"
The Herculoids (minus Igoo) have taken up a position overlooking the canyon. "There they are!" exclaims Dorno.
The ants swarm along their path. "I see them," says Zandor.
But the ants are turning; "They're heading the wrong way!" says Dorno.
"It's time to try and turn them!" exclaims Zandor. "We've got to steer them through this canyon!"
"Zok!" Zandor shouts to the airborne dragon, "Signal Igoo to start the avalanche!"
"I hope this works," says Dorno. "It has to work!" replies Zandor.
Igoo stands high on a rock formation overlooking the thick swarm of ants, a boulder clutched in his massive paws. He hurls the boulder against a cliff…
…causing a landslide that sends tons of rock and rubble crashing down.
Another boulder, and another landslide; Igoo roars with pride at his handiwork: a veritable wall of rock that blocks the ants' progress.
They pause at the rockslide; then, as one, they turn aside. "It worked, Zandor, it worked!" exclaims Tara. "They turned!" adds Dorno.
"Yes, but not enough!" Zandor replies. "You wait here!"
"Where are you going?" asks Dorno. "To turn them!" answers Zandor.
Standing on a rock overlooking the marching ants, Zandor unleashes a barrage of energy rocks from his slingshot. Those ants not destroyed outright turn away from the attack.
Dorno, sitting atop Tundro on the canyon floor, with Gleep behind him. points out Zandor's success. "He did it, Tara! They're heading this way now!"
Tara, standing on a rather precarious ledge of rock, responds, "Yes! Now you'd better get back out of the way!"
"Good job, Igoo!" Zandor says to his rock ape friend. "Now let's get back. They're almost at the bottom of the canyon!"
"Look out, Tara!!" Dorno shouts, just as the rock ledge crumbles under her feet, pitching her directly in path of the oncoming ants!
Gloop stretches down, surrounding Tara with his body just as the ants reach them.
"Come on, Tundro! We've gotta save her!" says Dorno. Tundro charges the column of ants, knocking some of them out of the way. "We're coming, Tara!"
Tara pokes her head and arms up from Gloop's protection. "Dorno!"
From Tundro's back, Gleep stretches out to grab Tara's wrists, lifting her up out of the way of the ants and onto Tundro's back.
"They made it!" exults Zandor. As Gloop takes his place beside Zandor, Zandor remarks, "If they keep going, we've got this battle won!" A puzzled Dorno asks, "What do you mean, Zandor? How?"
Zandor points. "See that end of the canyon? Well, that canyon leads directly over the Bottomless Cliffs.
"They'll march to the last ant into that darkness!"
"Has it ever happened before?" asks Dorno.
"Yes," replies Zandor. "And we can only hope it never happens again!"
Oh boy, does this episode raise questions it never answers! Unlike most of the enemies the Herculoids have faced, these ants are a "home-grown" menace. But are they a "natural" menace? Were these normal-size ants that were somehow mutated by the lightning bolts into the giant-size horror seen here? That doesn't seem likely, since we never saw the eggs grow. Zandor apparently has knowledge of at least one other "infestation" of the destroyer ants that's happened in the past, but it still seems that this ant invasion was not "normal" behavior.
And exactly what role did the lightning play in the story? My theory: the writers felt they needed something that seemed to explain the emergence and rampage of the ants, and electric bolts fulfill that purpose nicely (or so they thought). And once again, the fact that this series was aimed at children, and that the stories are so short, result in (I think) the writers feeling that not much explanation was needed.
Hordes of rampaging ants (giant or normal-size) have been a staple of adventure fiction for decades (if not centuries). The iconic "killer ant" story is probably "Leinengen Versus the Ants" by Carl Stephenson, published in 1938. In this classic short story, Leinengen is warned that a swarm of ants "ten miles long, two miles wide… and every single one of them a fiend from hell!" is marching toward his Brazilian plantation, destroying everything in its path. Leinengen, however, believes that "the human brain needs only to become fully aware of its powers to conquer even the elements"; therefore, instead of fleeing, he decides to make a stand against the ants.
"Leinengen Versus the Ants" was adapted into one of the best-known episodes of the popular radio series Escape, starring radio veteran (and later star of the TV series Cannon and Jake and the Fatman) William Conrad, whose sardonic chuckle "Meh-heh!" sums up the character's defiant nature perfectly. The short story later became the basis of the movie The Naked Jungle, starring Charlton Heston as Leinengen (and, amusingly, features Conrad in the role of the District Commissioner who pleads with Leinengen to save his own life and abandon his plantation.)
So it's only natural that a killer-ant story show up in the Herculoids canon. And, once again, a little more thought given to plot - and maybe a longer running time - could have elevated the episode from poor-to-mediocre to classic.
The "Oh, Come ON!" moment happens at the very end, when the ants stampede themselves over the canyon wall into… the "Bottomless Cliffs"? Sorry, even as a child I never bought the concept of a "bottomless" anything: cliffs, pits, oceans, etc. Such a thing is physically impossible, although the idea that something could be so deep as to seem bottomless is plausible.
And somewhat in the same vein: looking over these episodes now not only as an adult with (I hope) better developed critical facilities, but as an artist who had at one time seriously considered a career as an animator (largely inspired by series such as Herculoids and Jonny Quest, I find myself almost heartbroken over how poorly drawn a lot of these cels are. Besides the usual culprits of rushed production schedules and low budgets that work against the crafting of even competent art, part of the problem may be that many of the artists had never had extensive experience with drawing or animating anything but the "funny animals" of Yogi Bear or Huckleberry Hound, or the humorously stylized humans of The Flintstones and The Jetsons. Look, for example, at this cel of Dorno, Gleep, and Tara sitting on Tundro's back, just after Tara's rescue from the marauding ants:
Take note of the fact that Tara as drawn here looks like Dorno's twin sibling, instead of his mother! And unfortunately, there are many more examples of rushed or shoddy drawing than there are of exemplary art. It makes me wonder if Bill Hanna and Joe Barbera even looked at these cartoons on which they insisted their names appear as producers and directors.
I am pleased, however, with how much screen time Tara gets in this episode; I'm guessing that a third to a half of all of the lines Virginia Gregg recorded for the series are used in this one episode. (Which isn't to say she has a lot of lines in this episode, more that she has so few lines in most of the others.)