Category Archives: Prairie Insects

Japanese Beetles in Prairies – How Much Should We Worry?

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Japanese beetles (Popillia japonica) first appeared in the U.S. back in 1916 (in New Jersey) and have been spreading west since then.  They’ve only started to be abundant in our part of Nebraska during the last several years.  As a result, I’m not really sure what to expect in terms of potential impacts to our prairies.  I’m largely writing this post to hear what my friends to the east have been seeing, since the little buggers have been around there longer.

Japanese beetles are known pests of gardens and crops, but what are their impacts in prairies?  This one was eating the flowers from leadplant (Amorpha canescens)

While I’m not sure what to expect in prairies, our family has had plenty of experience with their ability to damage our garden crops.  Japanese beetles wiped out our raspberry crop last year and were trying really hard to kill our little apple tree this year.  I’m not a fan.

For those of you not familiar with Japanese beetles, they are about 1/2 inch long beetles that are metallic green with brown wing covers.  The series of white spots around the edge of their abdomen are actually little patches of white hairs, and those help distinguish them from lots of other metallic green beetles.  The larvae feed mostly on the roots of grasses, and they are a big pest in lawns and other turfgrass situations.  As adults they’re known to attack over 300 different plant species, with corn, soybeans, maples, elms, plums, roses, raspberries and grapes among their favorites.  Hence, they are pretty unpopular with gardeners and farmers alike.

Adults emerge in the early summer and seem to spend the vast majority of their time eating and mating – often at the same time.  Females take breaks from feeding/mating to burrow a few inches into the soil in grassy areas and deposit a few eggs.  Then they come back out and join the crowd again for a while.  They can repeat their burrowing/egg laying up to 16 times a season.  Most adults live for about a month or month-and-a-half, but some can live up to 100 days or more.  They are skeletonizers of plants, meaning that they feed on the portions of leaves between the veins, leaving behind only the skeletons of those leaves.

Japanese beetles skeletonizing leaves of Illinois tickclover (Desmodium illinoense)

I’ve been trying to pay attention to Japanese beetles in prairies, but I don’t feel like I’m learning very much yet.  The biggest infestations I’ve seen have been in the small prairies here in Aurora (Lincoln Creek Prairie).  In bigger prairies outside of town, I don’t see nearly as many.  At Lincoln Creek, the beetles feed on a lot of different plants, but seem to have special attraction to tick clovers (Desmodium) and the flowers of roundheaded bushclover (Lespedeza capitata).  However, while I’ve seen many plants nearly covered with beetles, many others manage to successfully bloom and make seed, so I don’t yet see the beetles having any major impacts.

Japanese beetles  feeding and mating on roundheaded bushclover (Lespedeza capitata)

Despite a heavy presence on Illinois tickclover flowers and leaves, many plants still produced seed this season, at least at Lincoln Creek Prairie in Aurora, Nebraska

Help?  What are those of you in the Midwest and further east seeing in prairies that have had decades or more of Japanese beetle infestations?  Any evidence that they might wipe out particular plant species?  Should we be concerned about them in our Nebraska prairies or just focus on protecting our gardens and crop fields?

Any advice is welcome – thank you.

Photo of the Week – August 16, 2018

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I’ve been spending a lot of this summer at Lincoln Creek Prairie, right across town from my house.  Much of my time there has been spent working on my square meter photography project, but I’ve wandered a lot through the rest of the prairie as well.  Visiting the same site frequently always helps me appreciate the dynamic nature of prairies.  I get to track individual flower blossoms as they transform from buds to blossoms to seed heads, and watch insects move from larva/nymph stage to adult.

Last weekend,  for example, I visited the prairie two days in a row and spotted four different Chinese mantises  that had just emerged from their last molt, leaving their exoskeletons behind.  I don’t think I’ve ever seen one of those exoskeletons before, let alone four over a two day period.  I’m guessing the skeletons don’t usually hang around long before they fall, dry up, and shrivel into obscurity – not necessarily in that order.

A Chinese mantid peers at me as I eased my camera toward it.  This one was photographed a few days before I found the exoskeletons and recently-molted adults.  

This is one of four shed mantis exoskeletons I found over a two day period.

One of my most exciting finds at Lincoln Creek this month was a small bee with gorgeous blue eyes.  It was a male Tetraloniella cressoniana – something I know only because I sent the photo to  Mike Arduser for identification.  I’ve photographed this species once before, back in 2009, and I wrote about it in a 2011 blog post.  The bee is noteworthy because it is very specialized in diet – feeding only on pitcher sage, aka blue sage (Salvia azurea).  Not coincidentally, that is the flower species in both pictures I have of this species.

Ever since learning about the species from Mike, I’d been hoping to see and photograph it again.  I finally got my wish last week, on a dewy morning at Lincoln Creek.  The bee was poised on a blue sage flower, probably waiting for the prairie to warm up and dry out enough that females would emerge from their nests.  I took quite a few shots of it as I gradually edged closer and closer, until it nearly filled the frame.  As soon as I got home, I fired off one of the photos to Mike, who enthusiastically identified it for me.

A male blue sage bee, which tolerantly allowed me to photograph it – only, I assume, because no females were available to chase.

Dewy mornings have always been favorite photographic opportunities for me, especially when the wind is calm.  Insects get trapped in dew drops, making them easy to photograph, and the entire prairie glistens and sparkles as the first light of the day hits it.  Photographing individual dew drops is always alluring, but rarely turns out very well for me – my macro lens doesn’t magnify them enough for my taste, and depth-of-field issues and slight breezes increase the technical difficulty significantly.  Now and then, however, I find the right situation.  That happened last week with a big droplet near a patch of sensitive briar flowers.

A dew drop and sensitive briar flower (Mimosa quadrivalvus) made a pretty combination.

Lincoln Creek Prairie has been a favorite spot of mine since I moved to town over 20 years ago.  It’s only about a mile from my house, and is a nice restored prairie with lots of flower and insect diversity.  The prairie is small and subdivided by tree lines and roads, but none of that really affects close-up photography.  Despite having made hundreds of trips to the prairie before this summer, though, I’m still finding new subject matter and making new observations – showcasing beautifully what prairies are all about.