Photosensitivity of Dispersing Cryptic Date Stone Beetles Coccotrypes dactyliperda (Coleoptera, Curculionidae, Scolytinae)-A Pilot Study.

Abstract

Simple SummaryDate stone beetles (Coccotrypes dactyliperda), which feed on the albumen inside palm seeds, are a major pest in date palm plantations in the Middle East and North Africa. While they spend most of their life cycle in darkness inside the brood galleries where they mate and reproduce, females emerge for a short period of time when the brood gallery has become too crowded or when the seed’s albumen has been exhausted. During this emergence they seek out fresh seeds, commonly by attacking unripe dates still on the palm. Previous work indicated that the beetles might prefer dark conditions (i.e., nighttime) when emerging from seeds, whereas anecdotal evidence suggested that the beetles might be attracted to light. The controlled experiments showed that the beetles, once in the open, are attracted by and move faster to a light source, but that the color of the surface (red, blue, green, black) has no influence on either direction or crawl speed.The date stone beetle, Coccotrypes dactyliperda, is a cryptic spermatophagus species that spends almost its entire life cycle inside the seeds of palms, esp. Phoenix sp. Only during dispersal, when the host seed has been largely eaten out, do females emerge for a short period of time in search of a fresh seed in which to establish new brood galleries. Previous work indicated that C. dactyliperda might be photophobic, preferring to emerge from seeds during night hours, whereas anecdotal evidence suggested that the beetles might be photophilic in terms of their movements post emergence. This paper examines the photosensitivity of the species under controlled laboratory conditions. The results show that C. dactyliperda, once removed from the brood chamber, is attracted by and moves faster to a light source, but that the color of the lit surface (red, blue, green, black) has no influence on either direction or crawl speed.