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Citizen Science...A big thank you!

6/29/2021

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Over 600 people responded to our survey, and many sent samples of lily beetle larvae to be dissected for parasitism. A first look at the data indicates that some areas where our biological control agents (non-stinging parasitic wasps) were released are now nearly free of the beetle. Gardeners in eastern Massachusetts and the Ottawa area are enjoying growing lilies again. We cannot yet say with certainty that the parasitoids are the sole cause of the lily beetle decline. Other factors come into play as well, such as gardeners pulling out their lilies. When lilies are few and far between, some dispersing beetles might not manage to find a patch of their hosts and die without leaving offspring. Then there's the impact of all that beetle-squishing gardeners have been doing. Add to the mix the vagaries of the weather--too hot, too cold, too dry, too wet--all these things affect population dynamics.

We will be analyzing our data over the summer, so please check back for updates!

The photo below shows another act of predation: a lacewing larva eating a lily beetle larva. The photo is from my garden in Ottawa. The only reason I have any lily beetle larvae at all is because a survey participant from Québec sent me an adult female and I let her lay eggs in my garden. Don't worry, I won't start a new Ottawa outbreak; all her offspring have been preserved in alcohol to dissect for parasitoids when my new microscope arrives!

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predation on adult lily beetles

6/2/2021

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We are one month into our North America-wide citizen science project and I am thoroughly enjoying reading every entry that is submitted even though I can't respond to every one individually (there have been hundreds). Some participants have sent great photos, including the one below, by Rick Parent:
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Two participants were fortunate enough to catch acts of predation on adult lily beetles. The party line is that lily beetles don't have any predators here in North America, leading to the population explosions in gardens and natural areas with lilies. Of course nothing is ever absolute in nature. Here are two great photos to show that occasionally, adult lily beetles do make a meal for native predators. The first is by Joelle Koller, who photographed this robber fly snacking on an adult lily beetle:
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And here is a ground crab spider with its meal, photo credit to Linda LaBonte:
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Notice how nicely the spider matches its background...great camouflage! In contrast, the lily beetle is bright scarlet. Bright colours typically mean that a prey item is toxic or distasteful to predators (warning or "aposematic" colouration), or that it is just pretending to be toxic (mimicry). Lily beetles may very well be chemically defended by sequestering the toxins present in lilies for their own defense. While lilies are not among the most toxic plants, they do contain defensive chemicals, as do all plants to some extent. To my knowledge, lily beetle defensive chemistry has not yet been studied. Too many potential projects; too little time!
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    Author

    Naomi Cappuccino was a member of the Department of Biology at Carleton University in Ottawa, Ontario, Canada. She is now retired and no longer updating this site.

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