Wolbachia are bacterial endosymbionts in arthropods and ¢larial nematodes. They cause thelytoky, which is a form of parthenogenesis in which females produce females without males, in hymenopteran insects. Infection of this parthenogenesis-inducing Wolbachia has been restricted to the order Hymenoptera, but was found in another insect order, Thysanoptera. A parthenogenetic colony of a predatory thrips Franklinothrips vespiformis (Aeolothripidae) possessed B-group Wolbachia. Male progeny were produced from this thrips by heat and tetracycline treatments. Males produced motile sperm, which were transferred to the female spermatheca by mating. However, the mating did not a¡ect the sex ratios of the next generation, suggesting that the sperm do not fertilize the eggs.

Mating behavior of the scarab beetle Dasylepida ishigakiensis was observed in a sugar cane field in Miyako Is., Okinawa, Japan. In field observations of tethered females on 6 February 2002, calling behaviors were observed only within 30 min of sunset time (18:25-18:55, JST), when light intensity decreased from ca. 500 lx to 1 lx. Mating was strongly affected by temperature: adults appeared and subsequent mating occurred when the temperature at 18:00 was higher than 18°C. Females appeared from the soil, flew to settle on sugar cane leaves and commenced rhythmical abdominal expansion and contraction. Males were attracted to the calling females from leeward, landed on or near the calling female, and immediately mounted. After genital connection, the male raised his legs and suspended himself with his genitalia. Mating lasted for ca 2 h. Most mated D. ishigakiensis females neither appeared from the soil nor attracted males until the end of March, so are considered monogamous. In contrast, males appeared from the soil after mating on evenings warmer than 18°C and probably repeat mating if females are available.

The life history of the white grub Dasylepida sp. was surveyed in a sugarcane field in Miyako Is., Okinawa, Japan. Adult flights were observed from early February to mid-March in 2001. Adults commenced flight just after sunset (at around 18:30) and mated. Sampling from the pots placed in the field on 19 April yielded 41.8% eggs and 58.2% first stadium larvae. Larvae sampled on 20 June, 2000 were found to consist of 33.3% and 66.7% of the first and second stadium larvae, respectively. On 22 August, 87.5% of larvae were second stadium and the remainder (12.5%) were third stadium larvae. The proportion of third stadium larvae increased and attained 100% by 30 November. In an excavation survey on 26 November, 2001, 11 adults (three females and eight males) and five pupae were found in the soil at a depth of around 45 cm. Pupae were found in the tunnel cavities. We believe that adults remain in the tunnels until the next February. In the rearing experiments at 25°C in the laboratory, the egg period was 23.6 d and the larval periods of the first, second and third stadia were 80.9, 91.8 and 335.8 d, respectively. These facts indicated that Dasylepida sp. has a two-year life cycle.

Two egg parasitoid species, Telenomus nawai and Telenomus spec. are similar morphologically but they have been treated as different species because of their different reproductive forms, arrhenotoky and thelytoky. Male progeny were produced from the thelytokous colony of Telenomus spec. (TT) by heat and antibiotic treatments. These males mated successfully with females of arrhenotokous colony of T. nawai (AT) and the females produced on average 19.1% males. This percentage did not differ from that obtained from AT females mated with AT males (19.4%). Diagnostic PCR indicated that TT is infected with Wolbachia; antibiotic treatments eliminated Wolbachia from TT. These facts suggest that Wolbachia causes thelytoky and Telenomus spec. (TT) is conspecific with T. nawai (AT).

Precopulatory behavior of the white grub beetle, Dasylepida ishigakiensis, was observed under laboratory conditions to determine the environmental factors controlling mating behavior, which is synchronized among individuals at dusk in the field. When light intensity was gradually decreased, both females and males sequentially started moving their antennae, legs and abdomen, then walking, and females rhythmically extruded their abdomen while males opened the elytra to fly. Pheromone release by females was suggested in a wind tunnel assay in which males oriented themselves to both intact and crushed bodies of females, but not of males. When illumination was suddenly turned off, precopulatory behavior of females and males was similarly induced but the frequencies of calling and flying behaviors were significantly reduced as compared with those observed when light intensity was gradually reduced. This result may suggest that gradual darkening is an important factor for their synchronized appearance from the soil and subsequent mating behaviors, including pheromone release in females and orientation flight in males. These behaviors were significantly suppressed at low temperatures below 18°C. This result supports our previous conclusion that temperature is the primary factor controlling the emergence and mating activity of sexually mature beetles in the field.