Photo submitted to Times Observer Many people collect and corral the brightly colored larvae around the end of each summer. They watch them undergo the metamorphosis that transforms them from the lime green, not-so-creepy crawlies to bright orange streaks that migrate to Mexico each winter. This year, people are finding a disturbing thing happening to their specimens. See page A-3.

Are your monarch caterpillars melting?

Many people collect and corral the brightly colored larvae around the end of each summer. They watch them undergo the metamorphosis that transforms them from the lime green, not-so-creepy crawlies to bright orange streaks that migrate to Mexico each winter.

This year, people are finding a disturbing thing happening to their specimens.

Most people who’ve raised monarchs from larvae to adult butterflies are shocked to see so many die off, seemingly without an explanation. Many of those people are pretty bummed about it, too, and wondering whether they’ve done anything to cause it.

John Fedak, a science teacher for over 20 years, has an idea of what might be happening.

“It sounds to me like a viral infection,” said Fedak after being told the symptoms of a large butterfly population in a tank.

A butterfly enthusiast had monarchs in chrysalises of all stages — from only half-formed to fully-formed, and apparently healthy, still bright green and opaque — suddenly turning black and liquefying, oozing onto the tank floor and everything beneath them. Chrysalises were falling from the ceiling of the tank, and some of the caterpillars hadn’t even begun to form a chrysalis before going from bright green and yellow to dull brown and then black. Of a large population, around one third of the caterpillars had already died, and another third of what was left weren’t looking too good.

The virus Fedak suspects is Nuclear Polyhedrosis. And he had an analogy to explain how it can decimate a monarch population.

“Basically all of the caterpillars have some of this virus in them all of the time,” he said. “But it’s like a cold or flu virus. When it gets to a point that it overwhelms the system’s ability to manage it, it kills them.”

The virus, according to Fedak, is one of the more contagious ones that affect monarchs.

“NPV kills caterpillars in or out of a chrysalis,” said Fedak, “and as they die, they contaminate all the others.”

The entomological equivalent of one kindergartener with an influenza virus leaving the entire classroom puking for days.

Only rather than grounding the monarchs for a day or two of feeling funky, and then getting back to life, Fedak said this virus basically digests the caterpillar from the inside out, liquefying the cells and causing the telltale strings of black, green, and brown descending from the hanging carcasses.

According to “When Butterflies get Bugs: The ABCs of Lepidopteran Disease,” an educational resource available on the Emory University’s research archives, written by Sonia Altizer and Jaap de Roode, NPV is actually a little ickier than a cold or even the flu.

“These pathogens win the distinction of behaving like the Ebola virus of the insect world,” writes Altizer and de Roode. The virus is picked up from the environment, usually from the milkweed the monarch spends its entire larval stage eating relentlessly. As the virus reproduces, rapidly and relentlessly, within the cells of the caterpillar, the fluid that leaks onto the caterpillar’s surroundings provide a host of new viral particles that are easily ingested by the next caterpillar to come along.

It’s a pretty big bummer, for caterpillars and for those who look forward to this season, specifically because of the enjoyment they get from feeding their monarch habit.

Fedak is one of those.

He raised around 150 of the insects this year, and saw only minimal casualties from pretty unremarkable causes. Anyone who’s ever raised a handful of monarchs is likely prepared to see one or two of the chrysalises turn black and die during the process. What most people are not used to is the sight of a veritable monarch plague that’s colloquially known in entomological circles as “Monarch Black Death,” or “butterfly melt.”

Fedak said he’s had some people tell him of the same situation with their monarchs this year, and while hiking in Bradford last week he came upon a population that appeared to have died of NPV. He credits the damp environment and cool temperatures with this year’s apparently high incidence of monarch NPV die-off, but said he hasn’t done any scientific investigation to confirm his hypothesis. Still, with a 25 year history of teaching environmental science, biology, and ecology among other things, his is a pretty solid hypothesis backed by plenty of experience from which to draw.

NPV is pretty significantly devastating, particularly in captive populations with limited ability to distance itself from contaminated environments and food supplies. Symptoms of NPV infection in monarchs, according to butterflyfunfacts.com (which is one of the more reputable sources on monarch apocalypse research), include eating less than healthy caterpillars, becoming “soft to the touch instead of feeling like a nice firm caterpillar,” becoming sluggish, and a tendency toward an oily sheen before they die. The behavioral symptoms are sometimes the first things that experienced monarch handlers notice.

Most monarchs spend much of their entire larval stage on the same milkweed plant, or close by in clumps of the weed that grows on roadsides, in fields, and along treelines at the edge of open land.

It’s unusual for them to crawl up toward the top of the container they’re kept in until they’re ready to begin forming a chrysalis, at which point they typically head for the highest point they can reach, which is almost always the lid of the container. Larvae with NPV, however, may only make it halfway up the wall of the container, or less, before attaching to the surface and attempting to form a chrysalis. Once it reaches its terminus, regardless of where in the container that happens to be, an NPV-infected specimen will often hang in an inverted V shape, from its middle legs, or in a straight line, hanging straight, head down.

Once dead of NPV, the specimen will then liquefy and ooze onto whatever is below it, infecting everything it touches. Rain or water in the container will splash the viral remains of the specimen. So don’t let your dead leaky caterpillars get wet.

That would be bad news indeed.

Anything that lands where the caterpillar juice has been tracks it to wherever it lands next, and next, and next. And pretty much anything attracted to dead animals, like flies, will be attracted by the foul stench of a dead monarch, according to butterflyfunfacts.com. According to that site, one caterpillar can contain one billion virus particles, meaning that an entire population of NPV victims can spread the virus exponentially.

Interestingly enough, NPV is insidious enough, and also picky enough about what species it kills off, that it’s actually bottled and sold as a pesticide.

So what do you do if your monarchs are sinking faster than the Titanic and ruining all your nerdy science fun this fall?

Triage and damage control, recommends Fedak. Remove all of the caterpillars from the tank and never use that tank again.

For anything.

Separate out any clearly terminal caterpillars and euthanize them.

You need to decide what kind of karmic debt you can realistically afford before deciding how to do that, but butterflyfunfacts.com suggests freezing them in a plastic bag.

That site also suggests washing all containers in a solution of five to ten percent bleach if you’re planning to reuse it, which Fedak doesn’t advise. Any caterpillars that seem plump, firm, and are eating well can be tentatively salvaged in a separate container, but don’t have unrealistic hopes. NPV is a pretty serious destructive force, entomologically speaking.

The good news is that it’s not too late to find new monarchs, and as long as you’re not putting them in a contaminated container; you’re not doing anything to put them at risk for NPV.

All milkweed fed to monarchs should be rinsed under running water, and caterpillar feces, as well as day old milkweed, should be removed and the tank wiped clean with as little disruption to the precious larvae as possible. Monarchs prefer common milkweed to the swamp and butterfly weed milkweed, which are also native to our region, Fedak said.

Fedak said it’s hard to tell when any given monarch season will be over, but added that he’s seen monarchs still hanging around as late as October.