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The use of pheromones to disrupt mating behaviours is perhaps the most promising method for controlling the sugarcane pest Dasylepida ishigakiensis Niijima et Kinoshita, also known as the white grub beetle. Herein, based on laboratory observations of mating, oviposition and hatching behaviours in the white grub beetle, we suggest guidelines for the timing and length of sex-pheromone release in the field. In the present study, we collected virgin female adults early in the mating season (4 February) in sugarcane fields in Okinawa, Japan and mated them in the laboratory after different time intervals with males collected at the same time. We investigated the effects of delayed mating on mating success, timing of oviposition, female longevity after mating and progeny hatchability. Mating success – defined as the proportion of mated females that produced progeny – and hatchability were not significantly affected by mating delays of less than 31 days, although further delays dramatically decreased these parameters. Female life span and the time between mating and oviposition were unaffected by mating delay. Similar results were obtained for laboratory-reared adults mated on day 45, 60 or 80 after adult emergence. Based on these findings, we propose that releasing synthetic sex pheromones between mid-January (i.e. shortly before the start of the mating season) and late March would be optimal for disrupting the mating behaviours of this beetle in the field. [ABSTRACT FROM PUBLISHER]

The subtropical scarab beetle, Dasylepida ishigakiensis, has a two-year life cycle. This study showed the time of adult emergence from the soil relative to the time of dusk and the presence of the female sex pheromone. Beetles collected on Miyako Island were transported to Tsukuba where they were immediately placed under natural day lengths in February. They exhibited two emergence peaks that corresponded to the times of dusk in Tsukuba and on the island, respectively. Males emerged precociously if a lure containing synthetic female sex pheromone was placed in their container, whereas the females' behavior was unaffected. Previous observations that mated females dig deeper in the soil than virgin females, males or mated males were confirmed. To explore the underlying mechanism controlling the behavioral change associated with mating, liquid material derived from the male accessory glands, seminal vesicles and female bursa copulatrix was injected into beetles, but without any significant influence on burrowing behavior. No significant influence was also observed in beetles injected with anisomycin, an inhibitor of protein synthesis related to memory in other animals. [ABSTRACT FROM AUTHOR]

In order to understand the visual orientation mechanisms of the male black chafer Holotrichia loochooana loochooana to females, we examined male behavioral response to colored objects (lures) when female sex pheromone was present. In the field, males landed more frequently on darker lures than on lighter ones of the same color. Among lures of different colors but with the same brightness, males preferred landing on black, blue, or red ones to green or grey ones. The reflectance intensities of preferred lures were weaker than those of green and grey in the range of 540-580 nm. This range is considered to affect choice by males. When females perch on the leaf edges of the food plant to adopt a calling posture, the dominant background color is that of the leaves (i.e., green). This means that the landing target forms a silhouette (dark spot) which is prominent against a background of green leaves, providing maximum visual acuity for mating. [ABSTRACT FROM AUTHOR]

Adults of the white grub beetle Dasylepida ishigakiensis Niijima et Kinoshita (Coleoptera: Scarabaeidae) emerge from the soil around dusk for mating on subtropical islands. The present study examines the factors controlling the emergence of males in the laboratory. There are two steps involved. Standby behaviour (i.e. insect head appears at the soil surface) can be observed for several hours before the beetles actually emerge for mating. The standby behaviour is facilitated by warm conditions, although the proportion of standby individuals is influenced not only by the temperature on that day, but also by that on the previous day. Experiments in which beetles are exposed to photoperiod and thermoperiod combinations, in and out of phase, show that temperature is more important in inducing standby and emerging behaviour than light alone. For the second step, factors such as temperature, light and the presence of the female sex pheromone determine whether males will leave the standby position and emerge onto the ground. The female sex pheromone stimulates standby beetles to exhibit emerging and wing vibration behaviours, although the effect depends on when it is presented to beetles. Beetles burrow back into the soil; this behaviour is influenced by illumination and time of the day but not by temperature. The results suggest that D. ishigakiensis possesses a sophisticated mechanism controlling male emergence from the soil. [ABSTRACT FROM AUTHOR]

The present study investigates the emergence of adult white grub beetles Dasylepida ishigakiensis Niijima et Kinoshita (Coleoptera: Scrabaeidae) from soil as well as their burrowing behaviours. ‘Standby behaviour’ (i.e. adults come to the soil surface where they expose their heads) is shown in the field and, along with emergence behaviour, is entrained by LD photocycles. These 24-h rhythms persist after transfer to continuous light conditions for 2 days. By contrast, beetles transferred from LD photocycles to continuous dark conditions fail to show standby behaviour; thus, it appears to be manifested only in the presence of illumination. Under dark conditions, beetles emerge completely from the soil directly at the time when standby behaviour is otherwise expected to occur. Emerged adults then burrow back into the soil before dawn. Virgin and mated males, as well as virgin females, which are expected to emerge from the soil for mating on later evenings, burrow to a relatively shallow depth (<2 cm), whereas mated females burrow deeper (2–10 cm). Soil properties such as moisture, grain size, topography and temperature influence the burrowing behaviour and the depths that the beetles reach. [ABSTRACT FROM AUTHOR]

The white grub Dasylepida ishigakiensis has a 2-year life cycle and spends approximately 9 months as a nonfeeding larva, pupa and adult on a subtropical island. Evidence is presented indicating that this beetle has two diapauses that appear to synchronize this long life cycle with the seasons. Larvae exposed to 20, 22.5, 25 and 27.5 °C late in the third (last) stadium pupate rapidly except for some individuals kept at the highest temperature. The latter pupate upon transfer to 22.5 °C, indicating that larval diapause is maintained at high temperature but terminates upon transfer to a lower temperature. Pupal development is directly temperature-dependent in the range 20–30 °C. Adults develop reproductive organs (i.e. the ovary in females and the seminal vesicles and accessory glands in males) rapidly at 15 and 20 °C, whereas those kept at 25 °C take a long time to do so. Ovarian development is completely suppressed at 30 °C but initiated upon transfer to 20 °C. In the laboratory, males with well-developed reproductive organs mate even with sexually immature females , whereas females with undeveloped ovaries show no sexual behaviour. Although the two diapauses of this species are thermally regulated (i.e. a characteristic commonly expressed by insects in summer diapause), adults of this beetle emerge from pupae late in the autumn and remain in the soil for 2 months. Adult diapause effectively serves to synchronize the time of sexual maturation with the coldest month of the year. [ABSTRACT FROM AUTHOR]