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Dig It! Garden Blog

Backstage at the Butterfly House

If you’ve spent time in our Native Butterfly and Moth House this summer, you’ve probably noticed some changes there. Built vestibules now flank the entrance and exit of the House, and if you’ve wondered why, it’s because we’ve brought in butterfly and moth species from other parts of New England.

The vestibules are a necessary, added protection against winged-creature escapes and escapades. Another necessary component of “importing” our New England neighbors is a USDA-certified rearing room. Sound a bit intense and sci-fi-esque? Well, it is, in a way—especially when the rearing room is guarded by a large “Access is to Authorized Personnel Only” sign.

Inside, it only gets more fascinating. On tabletops around the room sit cages from which the only sound, if the room is quiet, is caterpillars noisily munching on leaves.

“If you’re in here alone, it is a bit creepy,” laughs Butterfly House Specialist, Alicia Miller, as she gives me a tour of the rearing room. The first two mesh cages contain mourning cloak butterflies—about 50 of which have just emerged from their chrysalides and are hanging upside down, Halloween-bat style, from the roof of the cage.

“We’ll take these guys out to the butterfly house today, and then they’ll overwinter in the outdoor rearing house. We’ll have to construct a wall of bark for them.” That’s where mourning cloaks spend the cold months—burrowed under bark or woodpiles.

“I also just gathered these eggs from the butterfly house,” she says, showing me a container of leaves, most of which are dotted by tiny reddish-brown spheres. “They’re pipevine swallowtail eggs. We’ll rear them in here, away from the threat of parasites, so we can repopulate the butterfly house next year with disease-free specimens.”

“The danger of parasites in the House is high,” adds Andy Brand, Curator of Living Collections. “The mesh keeps the butterflies and moths in, but it’s not fine enough to keep parasitizing species of flies and wasps out.”

That’s the main reason the rearing room exists. “We had to create it in order to get our USDA permit,” explains Andy. “The separate rearing room prevents the release of parasites. We bring our various species in here to keep new pathogens from being released in Maine.” The room features extra safety measures like a special self-closing door and minute mesh over the vents to prevent parasites from entering the duct system, should they escape from the fine mesh of the cages. Additional precautions against disease and contamination include sterilizing all containers and instruments in a 10% bleach solution, putting fine mesh over sink drains, and either bleaching or freezing for 72 hours any contaminated specimens.

“It’s quite common, parasitization. The caterpillar will pupate and then, instead of a butterfly or moth, a fly or wasp emerges,” he explains. “The most dramatic are sphinx moths when they get parasitized. The parasitic wasp lays eggs in the caterpillar. Those emerging wasp larvae eat the caterpillar from the inside, create cocoons on the caterpillar, which is still alive by the way, then the wasps hatch out. Once they emerge, the caterpillar will soon die.”

Part of the room’s prevention strategies is a pupa cabinet. Like an exhibit from a natural history museum, this white-painted cabinet constructed with mesh panels and a Plexiglas window in the front door, contains chrysalides of every sort, some on the cabinet floor waiting to be pinned up for the long metamorphosing season, some already attached to small branches. “This is why we need this room,” Andy adds. “Rearing them in a controlled space means we can safely repopulate the House.”

“Right now,” says Alicia, “the cabinet contains a variety of moths and butterflies. In the room at large, we have mourning cloaks, black swallowtails, American ladies, tiger swallowtails, painted ladies, and then we also bring in caterpillars we find on trees in the Gardens and rear them here.” Some recent examples include tussock moths, rosy maple moths, and silver-spotted skippers. “The funky ones,” she adds, “the cool ones, we let them get big and put them on the Discovery Cart in the House so visitors can see them.”

“Like these,” Andy says, opening one of the small plastic containers. “We found these unicorn caterpillars on the trees in the parking lot.” And, indeed, with one horn coming from the tops of their heads, these nascent moths really do look like little unicorns.

“Or this one,” he picks up another container. “This is the cleft-headed looper—it looks like a stick with a cat face.” Andy holds up a small branch from which emerges—if you didn’t know better—a stick at a 30-degree angle. Camouflaged so successfully, you have to look closely to realize that this stick is, in fact, a caterpillar holding on with its front legs, the rest of its body growing up and out from the main branch.

“This eastern tiger swallowtail caterpillar is new,” says Alicia, showing me a photo of the green specimen. “The crazy thing is, we put him on a cherry on the Discovery Cart, and the next day, we found him on a cherry tree on the other side of the house.”

The butterfly crew also puts sleeves on trees in the Gardens. If you see these on your visit, know that these are temporarily housing some of our friendly caterpillars, tucking them away from parasites until the staff can move them to a new branch or tree. Once they pupate, they’ll be brought inside the rearing room to finish their metamorphosis.

“It’s a busy place,” Alicia says, looking around. And indeed it is—for the inhabitants as well as their staff, if the eerie, constant sound of leaf-chewing is any indication.