Chris Randall thought that if monarch butterflies were going to shlep all the way to Massachusetts, the least he could do is save their offspring from the mower’s indiscriminate blades.

“If you’re going to come up from Mexico only to have your children chopped up, I just think that’s a travesty,” said Randall, a science writer who clearly enjoyed the sensational image he evoked. “The least I could do is look at the milkweed plants.”

This summer, for the 16th year, Randall rescued tiny monarch eggs by plucking the milkweed on which they had been laid from a field near a house he visits annually in Southeastern Massachusetts.

“I’m just helping them to do their thing,” said the 56-year-old Concord resident.

After raising and releasing about 150 winged wonders, he delivered his last two late-blooming caterpillars to Susan Erickson’s fifth-grade class at Thoreau Elementary School in Concord.

On a recent morning, the two caterpillars were busy at work in their temporary aquarium feasting abode. One was on milkweed (monarch

caterpillars feed solely on the plant, which gives them an unpleasant taste that discourages some would-be predators), while the other was attaching itself to the aquarium’s ceiling, preparing to form a jade-green chrysalis as the next phase in its famous metamorphosis.

As students filed into Erickson’s classroom, 10-year-old ­Lila Hempel-Edgers marched over to the aquarium and announced: “The caterpillar’s in the ‘J’ shape!”

A few classmates crowded around the aquarium to get a look at the yellow and black caterpillar that was indeed curled into a hook, as it attached itself with silk and began to form the chrysalis.

“I think it’s pretty fascinating, the stages they go through,” said George Howes, another fifth-grader.

Randall said he has always been attuned to nature, and started collecting monarch eggs when his two daughters, now college age, were little girls.

“The thing people should know is it’s really easy,” said Randall. “Milkweed is really easy to spot. The eggs are easy to spot. This is something families can easily do.”

The eggs are tiny, maybe the size of a sesame seed; Randall collected his in July. But they can be found on the underside of milkweed leaves in Massachusetts from roughly June through mid-August, depending on the year, he said.

Then, Randall just makes sure they have plenty of milkweed, which he stands up in old sippy cups so the plants get water, as they hatch into caterpillars. After that he watches and waits as they become adult butterflies and are ready to fly away.

He likes to house them in an aquarium, Randall said, but a smaller plastic container would work, as long as there is enough room for the caterpillars to hang down when they are ready to start their transformation. Without a container they might find a way to hang onto the milkweed or look for a convenient ceiling or table to hang from, he said.

One of his daughters, Emma Randall, 19, said she used the annual experience as the subject for a college essay, comparing the journey from egg to butterfly to her own transformation from child to young adult.

“I wrote about it as a metaphor, metamorphosis for me, kind of going through when I was younger and being really excited about it and having that be this really amazing miracle,” she said. “And then going through high school and losing interest in it and coming back now and getting the same excitement from it, just coming full circle.”

That’s right, not even butterfly enthusiasts are immune to the ennui of adolescence.

“In middle school there was definitely this kind of, like, ‘Oh I’ve done this before,’ ” said the younger Randall, now a sophomore at Santa Clara University in California. “ ‘Oh, my dad collects butterfly eggs and raises them,’ and people were like, ‘That’s really cool,’ and I’m, like, ‘Yeah, whatever.’ ”

Now, she said, she admires her father’s persistence. He spends hours scouring the same field each year, determined to examine every milkweed plant and find each egg before the mowers rev up.

So what will happen to the two soon-to-be butterflies in Erickson’s fifth-grade class?

According to monarch authority Dick Walton, also a Concord resident, if they emerge soon, they will have a “decent chance” of making the 2,500-mile flight back to Mexico, their wintering ground.