The Transformed Block Count

by Carl Strang

The developers who built my subdivision, in their wisdom, decided to plant mostly green ashes along the streets. That brilliance has been answered in the form of an insect, the emerald ash borer. This little invasive ash-killer has done a number on my neighborhood. A series of before-and-after shots follows, going around the block route I follow when I do my standard survey of singing insects in the warm months.

Looking north along my street in 2009.

Looking north along my street in 2009.

The same block now.

The same block now.

Turning west in 2009.

Turning west in 2009.

Same view, 2013.

Same view, 2013.

The next block, looking south in 2009.

The next block, looking south in 2009.

And now.

And now.

The final leg, facing east in 2009.

The final leg, facing east in 2009.

Hard to believe it’s the same block today, but it is.

Hard to believe it’s the same block today, but it is.

Most of the tree loss happened over a brief period of time, the second half of summer last year. Ever the opportunist, I made predictions about the response of the three singing insect species common enough for statistical comparisons between this year and last. Greater angle-wings are tree-dwelling katydids, and so I expected their counts to drop. Carolina ground crickets mainly live beneath foundation shrub plantings, so I expected no significant change. Finally, striped ground crickets prefer sun-lit lawns to shade, so I expected their numbers to increase. I was correct on two of the three predictions.

The Carolina ground cricket median count in 2013 was 7, not significantly different from 2012’s median of 5 (Mann-Whitney U-test of the ranks of all the counts led to a z statistic of 2.05, p>0.01). The median count of striped ground crickets in 2013 was 20, that in 2012 was 11. The comparison of ranks produced a statistically significant z value of 3.89 (p<0.01). I was somewhat surprised at the lack of a demonstrable difference for greater angle-wings (z = 1.00, p>0.01). The 2013 median count was 3, less than the 2012 median of 5, but the difference was not as large as one might expect. There were enough surviving trees of other species to sustain a population of the katydids, and also the removal of the nearer trees made more distant angle-wings more audible.

Two Helper Wasps

by Carl Strang

Recently two new wasps appeared at flowers in the south stream corridor prairie at Mayslake Forest Preserve. It happened that one of them was featured in a recent post on Eric Eaton’s blog.

Bicyrtes quadrimaculata, so far seen only on common mountain mint flowers at Mayslake.

This is a tunneling solitary species that feeds its young paralyzed true bugs. Eric focused on one such prey, the marmorated stink bug (Halyomorpha halys), which has become an invasive pest of fruit crops. Though the wasp is supposed to dig only in sand, there is none at Mayslake, but perhaps there are some suitable spots along the little stream. I do not know if Halyomorpha has shown up in Mayslake’s old orchard, but the preserve no doubt holds a diversity of native true bugs the wasp can exploit.

On Friday another new wasp showed up.

Cerceris fumipennis, visiting rattlesnake master flowers.

As I reviewed some Internet references I found a site connecting this wasp with a different pest species. Cerceris likewise is a solitary tunneling wasp, but it focuses on beetles as food for its young. As this wasp has a taste for buprestids, it may have value in monitoring for emerald ash borers.

Bored

by Carl Strang

The emerald ash borer has become a common tree-killer in northeast Illinois. I knew it was likely that, sooner or later, the green ash in my front yard would become infested, and now it has happened. My tree held out longer than most of the ashes in my subdivision, but it was on the decline before the borers came along, and now the symptoms are clear.

The top branches are dying, and the tree is responding by producing a dense growth of lower shoots (only a small part of that bunch of green is the tree’s Virginia creeper vine). This is a typical pattern, as the beetles lay eggs in the top of the tree first.

I haven’t yet seen the diagnostic D-shaped exit holes made by emerging adults of these bark beetles, but one of the lower dying branches had several woodpecker holes which are a further clue.

There were a number of holes just like this one, made by a woodpecker extracting a larva.

So, sometime within the next few months I’ll have to have the ash removed, and I am contemplating what kind of tree to put in its place.

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