Dispersal Ability

by Carl Strang

In order for us to understand insects well enough to know which ones need the most attention in conservation, there are some pieces of information we need: how abundant they are, how broad or narrow their habitat needs, their reproductive potential, and their dispersal ability. The first two items are readily obtained in the course of a regional survey such as I am conducting for singing insects in northeast Illinois and counties in neighboring states. Reproductive potential has been studied to some extent and can be found in the literature for some species. Dispersal ability is a critical point that is not well studied as far as I can tell, and so it is good to take advantage of observations that reveal which species spread easily, and which ones do not.

Over the past two weeks I spent much time in the St. Joseph Hospital in Mishawaka, Indiana, where the medical professionals saved my mother’s life.

The hospital was built 3-4 years ago, and is surrounded by extensive areas planted mainly in native prairie plants.

The hospital was built 3-4 years ago, and is surrounded by extensive areas planted mainly in native prairie plants.

Occasionally I took walks along the paths, or made observations while arriving or departing. The species present in the plantings can be regarded as ones with high dispersal ability. These included field crickets (I cannot be sure which, as this was the cusp between the spring and fall field cricket seasons), striped and Allard’s ground crickets, Carolina grasshoppers, Roesel’s katydids, and a sword-bearing conehead. All of these are regionally abundant, and fairly broad in their habitat (dry to mesic mixes of grasses and forbs). Three have good flying ability (in the case of Roesel’s, there are long-winged individuals as well as medium and short-winged ones). Field crickets and the ground crickets can take advantage of their regional abundance and tendency to hop and walk over land. One limitation here is that I was only able to make observations over a brief portion of the season.

If I had to point to the weediest singing insect in our region, I’d have to say it’s the striped ground cricket, which is the quickest to appear in a new site.


  1. Nancy C. said,

    July 25, 2013 at 6:20 am

    Good topic – thanks for the idea. Since I’ll be starting a tree cricket observation acre next year (using several WI species that I’ll be transporting there) — I need to pay more attention to what is naturally there this year. Thankfully tree crickets sing, so I can do quick evening surveys in August and September.

    • natureinquiries said,

      July 26, 2013 at 5:56 am

      Thanks, Nancy. This is another important subject that, as far as I know, has not been investigated with any singing insects: introduction of species into new habitat areas. This could be one way to save or improve the status of rare species with low dispersal ability (the short-grass prairie cicada comes to mind as a possibility here).

      • Nancy C. said,

        July 26, 2013 at 7:24 am

        I’ve always assumed that I need to be very careful not to introduce species that have not been found in southeast WI – is that a correct assumption?

      • natureinquiries said,

        July 27, 2013 at 7:18 am

        Yes. It might also be illegal without a permit.

  2. Hal Atherton said,

    July 25, 2013 at 6:52 am

    Praying for your mother.

    • natureinquiries said,

      July 26, 2013 at 5:51 am

      Thanks, Hal, it was a scary time, but she is OK and recovering for now.

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