Recommendations for Treated - Area Choice Assays with Termites ( Isoptera ) Chris

The repellency of catnip (Nepeta cataria) essential oil was evaluated in a treated-area choice assay with subterranean termites (Reticulitermes spp.). It appeared that fewer R. virginicus were found on the treated portion of a Petri dish within a period of about 7 d; R.flavipes was not affected by the presence of the oil. The data collected from the control dishes, however, showed an unacceptably high Type I error rate (rejection of H,: n, = nu, when Ho is true, where n, is the expected number of termites on the treated side and n,, is the expected number of insects on the untreated side). The tendency of termites to cluster was the probable reason for this, and calls into question the data obtained from the tests. Computer simulations, using a range of cluster factors. replications and numbers of termites per replication, were conducted, and the Type I error rate was calculated when a cluster center (a point corresponding to a random angle 8 and radius p value within a circle) and random "termite" positions about the cluster center were plotted. Type I error rates were consistently inflated for all analyses that were based on individual animal behavior, and could not be corrected by increasing replications. We recommend an analysis where the number of insects on the treated or untreated side is recorded, then the dish is designated as "repelled or "not repelled," and the number of repelled dishes is analyzed. This method effectively controls the Type I error rate so that it is no greater than the nominal value. I t is recommended to use a t least 25 replications to ensure adequate statistical power. Analysis of these types of data is best accomplished by use of Fisher's Exact test or Boschloo's Exact Unconditional test.