by Carl Strang
In a recent post I shared the northward progress of jumping bush crickets in DuPage County. I thought I was done with them for the season, but their numbers seemed to increase over the past couple of weeks, and I was toying with making another check. The opportunity came on Friday. After work I drove up into Lake County to pick up my race packet for a half-marathon I was running on Saturday. On the way back I drove down along the Des Plaines River in Lake and Cook Counties, windows open on a reasonably warm evening. The result was a new north location for the species, just south of the split between Milwaukee Avenue and River Road in Cook County.
The pattern seems clear. Of the four major north-south rivers that provide the best travel corridors for jumping bush crickets, they have gone farthest north along the Des Plaines River, the easternmost. Next comes Salt Creek, which flows into the Des Plaines at the Brookfield Zoo. Most of DuPage County is drained by the two branches of the DuPage River, whose crickets are yet a little farther south. My earlier check of the Fox River, just west of DuPage, turned up no jumping bush crickets, but I started my search at North Aurora. Might they be a little farther south than that? Last night I checked that possibility, and found them abundant at Kendall County’s Richard Young Forest Preserve. Upstream (north) from there I found a lot of good looking but empty habitat, and then a pocket of the crickets just north of the town of Oswego, still in Kendall County (the lowest star on the map). They are within 2 miles of the Kane County border, but apparently haven’t reached that county yet. So, the northward advance of jumping bush crickets is marked by a line extending southwest from the northernmost red star in the map. It seems likely that they have spread up into northeast Illinois from Indiana, by way of the Kankakee River and perhaps by a broader flow through towns and preserves closer to Lake Michigan.