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Posts tagged ‘insects’


Why We Need Insects–Even "Pesky" Ones

Press Release 12-189
Why We Need Insects–Even “Pesky” Ones

Hard evidence of evolution: a five-year study shows that plants may quickly lose important traits through evolution soon after insects are removed from the environment

Photo of yellow flowers of evening primrose in Ithaca, New York.

A large natural population of evening primrose (yellow flowers) in Ithaca, New York.
Credit and Larger Version

October 4, 2012

View a video interview with Anurag Agrawal of Cornell University.

At first blush, many people would probably love to get rid of insects, such as pesky mosquitoes, ants and roaches. But a new study indicates that getting rid of insects could trigger some unwelcome ecological consequences, such as the rapid loss of desired traits in plants, including their good taste and high yields.

Specifically, the study–described in the Oct. 5, 2012 issue of Science and funded by the National Science Foundation showed that evening primroses grown in insecticide-treated plots quickly lost, through evolution, defensive traits that helped protect them from plant-eating moths. The protective traits lost included the production of insect-deterring chemicals and later blooms that gave evening primroses temporal distance from plant-eating larvae that peak early in the growing season.

These results indicate that once the plants no longer needed their anti-insect defenses, they lost those defenses. What’s more, they did so quickly–in only three or four generations.

Anurag Agrawal, the leader of the study and a professor of ecology and evolutionary biology at Cornell University, explains, “We demonstrated that when you take moths out of the environment, certain varieties of evening primrose were particularly successful. These successful varieties have genes that produce less defenses against moths.”

In the absence of insects, the evening primroses apparently stopped investing energy in their anti-insect defenses, and so these defenses disappeared through natural selection. Agrawal says that he was “very surprised” by how quickly this process occurred, and that such surprises, “tell us something about the potential speed and complexities of evolution. In addition, experiments like ours that follow evolutionary change in real-time provide definitive evidence of evolution.”

Agrawal believes that his team’s study results are applicable to many other insect-plant interactions beyond evening primroses and moths.  Here’s why: The ubiquitous consumption of plants by insects represents one of the dominant species interactions on Earth. With insect-plant relationships so important, it is widely believed that many plant traits originally evolved solely as defenses against insects. Some of these anti-insect plant defenses, such as the bitter taste of some fruits, are desirable.

“This experimental demonstration of how rapid evolution can shape ecological interactions supports the idea that we need to understand feedbacks between evolutionary and ecological processes in order to be able to predict how communities and ecosystems will respond to change,” said Alan Tessier, a program director in NSF’s Directorate for Biological Sciences.

“One of the things farmers are trying to do is breed agricultural crops to be more resistant to pests,” said Agrawal. “Our study indicates that various genetic tradeoffs may make it difficult or impossible to maintain certain desired traits in plants that are bred for pest resistance.”

In addition, oils produced by evening primroses have been used medicinally for hundreds of years and are beginning to be used as herbal remedies. Agrawal’s insights about pests that attack these plants and about chemical compounds produced by these plants may ultimately be useful to the herbal and pharmaceutical industries.

Agrawal says that most previous real-time experiments on evolution have been conducted with bacteria in test tubes in laboratories. “One of things we were excited about is that we were able to repeat that kind of experiment in nature. You can expect to see a lot more of this kind of thing in future. We will keep our experiment running as a long-term living laboratory. ”

More information about this study is available from a Cornell University press release.


Media Contacts

John Carberry, Cornell University (607) 255-5353

Lily Whiteman, National Science Foundation (703) 292-8310

Program Contacts

Alan Tessier, National Science Foundation (703) 292-7198

Principal Investigators

Anurag Agrawal, Cornell University (607) 254-4255

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2012, its budget is $7.0 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives over 50,000 competitive requests for funding, and makes about 11,000 new funding awards. NSF also awards nearly $420 million in professional and service contracts yearly.


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Tarrant County’s guide to Gambusia (mosquito fish)

This humble little Texas minnow is one of the primary resources used by cities to fight mosquitoes — and they do a very good job of it, too.   They don’t come in pretty colors and they never get very large (up to 2 inches for females) but each fish can eat over 100 mosquito larvae in a day.  This makes them an ideal method of controlling mosquitoes, since when they’re in the larval or egg stage, mosquitoes don’t move about much and they float on top of the water.  They’re easier for predators such as the gambusia to spot… and eat.  Once they hatch out and are flying around, they’re much harder to catch, even for quick chimney swifts and other birds that catch flying insects. And they are the mosquito control method preferred by many Texas cities.


But this year in North Texas, the much-needed fish were in very short supply due to problems with the hatchery, leaving cities scrambling to find other sources — or resorting to spraying techniques (which residents don’t like.)


For people interested in these fish, Tarrant County has a local stocking guide for city governments that can be applied on a smaller scale.

Homeowners with ponds can get these fish from Keller Fish Farms:


Defining Dallas: Where have all the butterflies gone?



A mystery has emerged in the past three weeks that may have a very simple answer — but an answer that we’re not aware of — and that’s the mystery of what happened to the butterflies?


The question arose last week when I was leading a group of kids on one of our nature hikes at Trinity River Audubon Center.   As part of the activity where we’re studying insects on the TRAC property,  they were engaged in trying to find certain common objects so that their team could make a “nature bingo.”  When I make these game sheets, I keep the objects simple and easy to find so that everyone can contribute to the overall success of the group.  Two of the things on the bingo list were “yellow butterfly” (the sulfurs, Phoebis sp) and “white butterfly” (Pieris rapae).  On the “harder but possible to find”, I also listed the Tiger Swallowtail and Monarch.  I figured that Monarch would be an easy “hit” for that day, since there had been a release of a group of Monarch butterflies at TRAC just the week before.


But when I talked to the group, they said they didn’t see any butterflies.  Then a second group made the same report.  In casually chatting to the other teachers, I discovered that no one had really noticed any butterflies around that week.


That was interesting.


So the next day on the insect hike, I took a group of kids out on a butterfly spotting expedition.  We walked for 40 minutes but only spotted two butterflies of any type (Sulfurs (Phoebis)).  There were no butterflies in the butterfly garden, which has nectar sources and water sources and was set up specifically by the Texas Master Gardeners to attract butterflies.  Once the kids left, I decided to satisfy my curiosity and hiked two other trails on the property.  During my 30 minute excursion I only saw two sulfurs plus a third butterfly that appeared to be one of the Nymphalinae.  I didn’t spot moths, though I saw other insects including wasps and the ever-present grasshoppers.


So where are they?


I mentioned this to others at TRAC and several answers were suggested that really didn’t satisfy me.  One was that they’d been eaten by the large group of swallows that we’ve had flying over the pond in the past week or so.  Although it’s a possibility, it doesn’t explain why ALL the butterflies (including the monarchs and the very tiny butterflies) are gone.  A second explanation was that it was too hot to fly.  While I initially dismissed that one, it turns out that butterflies apparently will hunker down in the shade when it’s too hot — but that doesn’t explain why they’re not out flittering around at 9am, when it’s an optimal temperature.


As far as I can tell, they breed throughout our summer season so we should have some butterflies during any given month.


The drought does have an impact on insects — among them, migrating tarantulas.  But no news source yet has mentioned drought and butterflies.


The next step is to check some of the host plants in the butterfly garden and look again — but as far as I can tell, the butterflies are getting scarce at Trinity River Audubon Center and right now I’m not sure what the cause is.

(reposted from my Science2.0 blog)


Defining Dallas: The Unexpected Life of Snakes


Red-eared Slider on Trailhead Pond at TRAC

Red-eared Slider on Trailhead Pond at TRAC

crossposted and updated from my original article at:

I have just come in from Third Thursday at Trinity River Audubon Center.  The anticipated speaker canceled and there were families there who wanted a program, so I did the “Turtle Talk” and then took them out for turtle watching and a nature hike.  I wish I’d thought to take the pond temperature, because I’m getting reports from others now that yes, turtles don’t bask when it’s too hot.  We saw nine tonight, in the water with just their noses poking out.  When I took the group to look at the one turtle nest we’d seen, someone discovered a second one not fifteen feet from that!  I’ll GPS all three of the known nesting sites so we can see if they come back next year.

This morning we had kids from the YMCA, and one of the fascinating things they discovered was a group of 8 or nine snakes in a puddle of water under the bridge, all sliding around rather furiously — but never leaving the water.  I missed this since I was giving the classroom lecture on “bugs” (basically any “creepy crawly”) but they took me out in the afternoon and we had a look through the binoculars.

There were several Yellow Bellied Water Snakes (Nerodia erythrogasterflavigaster.), a ribbon snake, and one that might have been the non-venomous diamond backed river snake ( — which didn’t want to hold still for photos or observation, and as they were in a puddle about four feet below the deck, we weren’t going to scale the fence and then try to work our way down to the ground just to identify the snake (we could easily identify the poison ivy right near it, however.  Lots of it.)  After a few minutes (and with the help of Scott), we determined that they were “fishing” for a shoal of tiny Gambusia (minnows, or mosquito fish) that had gotten trapped in the puddle as the pond shrank.  The fish were swimming frantically trying to get away, but there was no escape.  The pool grew smaller during the afternoon, as the snakes moving through it swept the water from the puddle onto the bank.  By evening there was only a patch of mud and a single very satisfied (and full) ribbon snake.  The Yellow Bellied Water Snake was in another larger pondlet (too deep to be a puddle but only about 8 feet long and 5 feet wide), looking pretty content.

Scott said he had pictures from last year, so this is not a unique occurance.  Hopefully we’ll see other examples of this (and hopefully I’ll have a camera in hand the next time!