Sick frits

Melt and Wilt. 

Zombie disease. 

Black Death. 

NPV, short for Nulcear Polyhedrosis Virus.

I've found a number of different names for what's sickening some of our Gulf fritillary caterpillars on a passionflower vine. Yes, they're dying again. I first reported on this phenomenon three summers ago ("I feel like a murderer," June 14, 2010) and again last year ("More caterpillar deaths..." March 30,2012). It's very frustrating. In 2010, I cut down the passionflower vine on which the affected cats were dying. That seemed to help. But I still see caterpillars sickening, blackening and dying. 

Last year, I also saw other caterpillar species dying to I posted a photo at Bugguide.net. That's "possibly a baculovirus, which causes caterpillars to liquefy and eventually splash new virus particles onto the leaf, which may then be consumed by more caterpillars," replied Ian Stocks. He pointed me to a 2003 academic article in the Journal of Invertebrate Pathology: "A newly discovered baculovirus induces reflex bleeding in Heliconius himera."

So what IS a baculovirus? Google the word, and Wikipedia's definition will make you yawn...The baculoviruses are a family of large rod-shaped viruses that can be divided into two genera..." (Wikipedia even has a disclaimer: "This section may be too technical for most readers to understand." AMEN!) 

Here's the rest of Wikipedia's definition: Baculoviruses have very species-specific tropisms among the invertebrates with over 600 host species having been described. Immature (larval) forms of moth species are the most common hosts, but these viruses have also been found infecting sawflies, mosquitoes, and shrimp. Although baculoviruses are capable of entering mammalian cells in culture they are not known to be capable of replication in mammalian or other vertebrate animal cells. Baculoviruses contain circular double-stranded genome ranging from 80–180 kbp."

Now THAT explanation sure helps understand what's afflicting our caterpillars....

From what I can gather (from sources like NPR, NewScientist and National Geographic), "the government" sprays a baculovirus on trees to control gypsy moth outbreaks. However, researchers involved in the project reported on in 2011 by the aforementioned sources were more interested in how the baculovirus affects caterpillar behavior.

Personally, I want to know if this so-called pathogen is spreading to other caterpillar species, namely our Gulf fritillary cats!    

I've emailed Dr. Kelli Hoover at Penn State's Entomology Department (who conducted the 2011 research) but as yet have not received a reply. I also messaged a researcher associated with the 2003 research on baculoviruses and Heliconius himera (Gulf fritillary) caterpillars. Dr. Boucias wrote me right back and asked that I send him a sample caterpillar! 

"I would agree that the images look like the insects are infected with a baculovirus," he told me. "I should be able to readily confirm if this in fact is the cause."

Stay tuned!