Photo of the Week – August 23, 2013

As we’ve been looking for bees lately, I’ve noticed the abundance of spotted cucumber beetles (Diabrotica undecimpunctata) in our prairies.  I’ve primarily noticed them because they are feeding on the pollen of flowers, and from a distance they look like a bee.  I can’t count the number of times I’ve crept up to a flower to see what kind of bee is on it, only to find that it’s just another cucumber beetle…

Spotted cucumber beetle on showy tick trefoil (Demodium canadensis)

Spotted cucumber beetle on showy tick trefoil (Demodium canadensis)

Spotted cucumber beetle has another name that will be very familiar to farmers – southern corn rootworm.  While it’s a native insect in North America, it has adapted very well to human agriculture and is now considered a pest in both crop fields (corn and other crops) and gardens (cucumbers and other cucurbits).  I’m hoping some of the readers of this blog can help me answer a couple questions I have about cucumber beetles.

1. Are spotted cucumber beetles more abundant in prairies now than historically because of the prevalence of nearby crop fields?

2. Do cucumber beetles have a significant impact on any particular prairie plant species or on the overall ecology of prairies?

As far as I know, cucumber beetles are just nicely adapting to human-dominated landscapes, and while I see a lot of them, their primary impact is that they keep fooling me into thinking they’re bees…

Photo of the Week – August 31, 2012

It seems like a good time to be a crab spider.  The drought has greatly reduced the number of flowers blooming in prairies, forcing pollinators to visit fewer flowers in greater numbers.  Previously, I’ve used the analogy of crocodiles in watering holes to describe crab spiders waiting in ambush on flowers.  To further that analogy, the drought has now dried up all but a few watering holes, and the crocs just have to sit and wait for the increasingly desperate animals to come to water.

A crab spider with the spotted cucumber beetle it just captured.

When I was photographing for my drought post earlier this week, I found this crab spider, which had just captured a spotted cucumber beetle.  The beetle was still struggling against the spider, but the spider was maintaining a tight grip on its head.  I didn’t stick around for the ending, but it assuredly didn’t end well for the beetle. 

If you’re a gardener who has dealt with these beetles on your cucumbers, melons, or other produce, you’re likely not shedding any tears over this photo.  Not only do cucumber beetles feed on the leaves and fruits of garden vegetables, they are also a carrier for bacterial wilt, which can also cause lots of damage.  However, unlike some garden pests, cucumber beetles are native insects who just happen to have found easy pickings in cultivated areas. 

Cucumber beetles are a very common sight on prairie flowers right now.  They are feeding on the pollen, but like most beetles provide very little actual pollination for most of those flowers.  While they’re not pests to the degree they are in gardens, these insects aren’t really doing those flowers much good either.  

On the other hand, they’re providing a good food source for crab spiders!