Roesel’s Katydid Quest

by Carl Strang

Earlier I featured northeast Illinois’ common native predaceous katydid, the protean shieldback . We have another predaceous katydid, an import from Europe, Roesel’s katydid. Here is a female. Note the general brown color, and the yellow-edged half-moon of black behind the head.

Roesel's katydid female 2b

This is a species of open prairies, meadows and roadsides, preferring a mix of tall grasses and forbs. Here is a male in singing posture.

Roesel's katydid b

There are two things to note in comparing the two photos. First, the female is recognized by the curved, bladelike ovipositor protruding from the back of her abdomen. A structure of this sort is present in all female crickets and katydids. Second, note the long wings of the male and the short wings of the female. This is not a gender difference, as either gender can have either wing length. The male’s singing structures are in the basal part of the wings, and are complete in short-winged individuals.

Range maps for Roesel’s typically show it in a fairly large area of the northeastern U.S. plus a separate, smaller area in northern Illinois. I expected to find it in DuPage County. It is indeed abundant here, and I have found it in Kane and Kendall Counties as well. Imagine my surprise two years ago when, riding my bicycle around Culver, in north central Indiana, I started hearing the distinctive flat buzzing songs of Roesel’s katydids. I interrupted my workout to find one, and confirmed its identity visually. I intended to begin exploring the extent of their range extension last year, but a bike fall in mid-June gave me a broken collarbone and rib, forcing a postponement.

Last week I took a couple vacation days and searched for Roesel’s in two additional Indiana areas. First I drove to North Manchester in Wabash County, home of Manchester College.

Manchester College 3b

I covered 25 miles of country roads on my bike, and found scattered Roesel’s both west and east of North Manchester. I collected a voucher specimen.

Roesel's voucher b

I’m not fond of killing insects, but in this case felt the need for a voucher to support my claim. For what it’s worth, the greatest concentration of them was at the intersection of county roads 1400N and 300W.

Roesel coll site 2b

I found a larger than usual area of unmowed mixed grasses and forbs there.

Roesel coll site 3b

That was the source of the voucher specimen. The next day I drove down to Logansport for another prospecting bike ride. In a 22-mile tour of Cass County roads from the Wabash River north, again I encountered Roesel’s katydids regularly along the way. As on the previous day there were plenty of spring field crickets, too, plus a number of common meadow katydids, the first I’ve heard this year.

Roesel’s song is a mechanical sounding buzz, lengthy but with occasional interruptions. Nothing else produces a sound like it so early in the season. The males usually begin singing around mid-morning (though on a hot day I have heard them as early as 7:15 a.m.), and continue through the heat of the afternoon. In northeast Illinois the earliest appearance I have noted was June 10 (in 2007), latest June 22 (last year). They continue into the second half of July (the latest I have heard one was July 28 in 2006). For recordings of the song, go here  or here . You also can see the conventional range map, which clearly needs updating.

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