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Citizen Science Brings Monarch Butterfly Parasitoids to Light

Posted on Tuesday, August 1, 2017 at 12:15 pm in Uncategorized

(Photo: Charlie Gatchell)

Thanks to volunteers like you, we now know more than ever about the flies that attack monarch butterfly caterpillars. Over the last 18 years, Monarch Larva Monitoring Project volunteers have collected and raised more than 20,000 monarch eggs and caterpillars, and monitored them for incidents of parasitism by tachinid flies.

A recent paper published in the Annals of the Entomological Society of America uses data collected by citizen scientists to delve into monarch-parasitoid associations and help discern between natural and human-driven impacts on monarchs and their population size.

“Our paper provides an unprecedented view of monarch-parasitoid associations across space and time. It documents the main parasitoid enemies of monarchs, their relative abundance and impact on monarchs, and how parasitism varies with host stage. This sheds new light on understanding monarch larval ecology,” says Dr. Karen Oberhauser, director of the University of Minnesota Monarch Lab and co-founder of the MLMP.

Research and analysis like this relies on the participation of citizen scientists throughout the monarchs’ range. With continued data collection, researchers hope to further analyze patterns in monarch parasitism over space and time.

“Contributing to a project like this is not only fun and interesting, but it also is deeply satisfying to contribute to our understanding of the natural world and hopefully make a difference in conservation of that world,” says Ilse Gebhard, a MLMP volunteer and co-author of the study.

A summary of results is provided below:

  • Overall, 9.8 percent of monitored monarchs were parasitized, though frequency increased through larval stages, with a maximum of 17 percent among fifth-stage larvae.
  • By far, the most abundant parasitoid species (75 percent of tachinid fly specimens collected) was Lespesia archippivora, currently known as a generalist parasitoid of several moth and butterfly species. However, the researchers suspect the species may represent a “complex” of multiple, closely related subspecies, one of which specializes in parasitizing monarchs. This will be a focus of future research, Oberhauser says.
  • Three of the tachinid species identified had not been previously reported as monarch parasitoids, one of which appears to be a new, previously unknown species.
  • The third most abundant parasitoid species collected (10 percent) was Compsilura concinnata, a species that was introduced to North America in the 20th century to control gypsy moth. Specimens sent in by volunteers in Texas represent the first recording of C. concinnata in that state.
  • The researchers found a small number of cases of multiparasitism, in which more than one tachinid species emerged from a monarch host, which had previously never been reported.

You can read the full article on the Annals of the Entomological Society of America website. To contribute to further research on monarchs and their parasitoids, participate in MLMP Activity #3: Estimating Monarch Survival!

The original press release associated with this paper can be found here.

“Tachinid Fly (Diptera: Tachinidae) Parasitoids of Danaus plexippus (Lepidoptera: Nymphalidae),” by Karen Oberhauser, Dane Elmquist, Juan Manuel Perilla-Lopez, Ilse Gebhard, Laura Lukens, and John Stireman, July 2017, Annals of the Entomological Society of America. https://academic.oup.com/aesa/article/doi/10.1093/aesa/sax048/3894089/Tachinid-Fly-Diptera-Tachinidae-Parasitoids-of

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