Figure 2 from: Fossen EI, Ekrem T, Nilsson AN, Bergsten J (2016) Species delimitation in northern European water scavenger beetles of the genus Hydrobius (Coleoptera, Hydrophilidae). ZooKeys 564: 71-120. https://doi.org/10.3897/zookeys.564.6558

Figure 2 - Measurement of the relative position of trichobothria on the elytra (character 2.1). Dorsal view of anterior part of the elytra, showing how several trichobothria encountered posterior to the scutellum were measured. Each relative position of a trichobothrium was measured by dividing the length from the 3rd row of serial punctures to the trichobothrium (a) by the length from the 3rd row to the 2nd row (a+b). The same was done with trichobothria in or near the 5th row of serial punctures. Image of Hydrobius fuscipes fuscipes.