Substrate-dependent colour variation along the Kāpiti–Taranaki coastline and biological notes on Actizeta albata (Coleoptera: Tenebrionidae)

Abstract

This study investigated whether colouration of the beetle Actizeta albata Pascoe, 1875 matches the sand substrate along the Kāpiti–Taranaki coastline of the North Island. In A. albata, colouration may vary from mostly white to mostly black. Specimens were collected from the black sand beaches of the Taranaki–Whanganui region and grey sand beaches of the Kāpiti region. The extent of dark patterning on each specimen was traced and then quantified in ImageJ. With this data, specimens from black sand beaches were found to be significantly darker than those from grey sand beaches using a Mann-Whitney-Wilcoxon test (p < 0.01). Although this pattern is consistent with cryptic colouration, another possibility is that the darker colouration is the result of differences in sand grain abrasiveness causing scales to be eroded more quickly, making the beetles appear darker in colour. Additionally, general biological observations of the genus Actizeta from fieldwork and keeping the beetles in captivity are also recorded.