For an insect species or an insect group, the body size is considered as one of the important characters. Especially, body length is a typical indicator of body size that is little affected by the sample preparation. Measuring the body length of insect by the conventional method, however, takes a lot of effort and time. Accordingly, it is hard to collect enough data to examine the size distribution thoroughly. Here, we developed a semi-automatic method for measuring the body lengths of weevils using techniques of image analysis. This method dramatically shortened the time to measure the distribution of the body lengths of weevils. In addition, we demonstrated that it was easily possible to collect enough data to examine the shape of the distribution in detail, such as asymmetry, by the method.

Cockroach specimens were collected using sticky traps at the borders of sidewalk, in Minato-ku, Tokyo, from May, 2012 to December, 2014. Periplaneta fuliginosa (Serville) was captured at all collection sites, and Blattella nipponica Asahina, and Asiablatta kyotensis (Asahina) were captured only at the borders of sidewalks along the canal. I captured 39, 32, and 36, cockroaches in 2012, 2013, and 2014, respectively.